Vinyl / 7" Single

Singles normally have one track per side, usually an A-side (sometimes marked as such) and a B-side. Double A-sides were sometimes used as a marketing ploy. Sound quality is never particularly good, as poor quality vinyl was commonly used. Running times are typically 3-4 minutes per side, any longer and the sound quality suffers. Although musically there is nothing by Deep Purple on single which cannot now be found on CD, many fans like to assemble a collection of singles from their own country. The format has almost entirely died out in recent years, though is still popular with new indie bands.

Vinyl / 7" EP (Extended Play)

Normally have two tracks per side. EPs were popular during the fifties and sixties as they were more affordable than albums, and came in laminated card sleeves. The format died out in the early seventies but was revived for limited editions at the end of the decade. Speed was normally 45 rpm but sometimes 33 1/3 rpm. Some nice Deep Purple EPs were issued in the UK after the band split. With cramminga lot of material into a small area, the sound level can be quite low.

Picture / Art Sleeve singles / EPs

In the UK and America singles were normally issued in paper bags carrying only record company label graphics as a cost cutting measure. In Japan and Europe however special sleeves with photographs of the artists (pic sleeve) or a graphic (art sleeve). Pic sleeves emerged in the UK in the mid-seventies (before this short runs or promotional editions sometimes had sleeves) after being made popular via the punk scene. Pic sleeves are still collected (though not so widely as before) and early or rare sleeves fetch high prices (£100 / $150 or more) especially if in good condition. The first Deep Purple single was 'Hush' and this carried a limited edition pic sleeve in America and also in the UK but only on promotional copies.

Promo / demo singles

Most single releases were preceded by a promotional edition, which carried the words 'Promotional Release', 'Demonstration Use' or something similar on the label. The Aside would be marked clearly and sometimes the date of release would be given. The label might be a different colour too. These releases would be in limited quantities and are sought after by collectors. In America mono / stereo couplings of the same track were issued for radio use as promotional items and most of the classic Deep Purple releases were available like this. The price of promos is dictated by rarity rather than content, so the edited Concerto tracks issued on a single in 1969 are of little musical value but the promo single will cost you a lot to buy.

Vinyl / 12" singles

Devised for use in discos in the mid seventies, the 12" single could carry a wider, and therefore louder, signal. Due to changes in chart regulations, labels began to issue 12" singles by most acts to help boost sales. In America special 12" promotional singles became popular for all pop and rock genres. They usually had special label graphics and often sleeves as well - either with centre holes to show the label, or regular album style covers. Deep Purple 12" releases from the first era are rare (there was a 'disco' version of 'Child In Tme' in Holland - just the normal studio take - and a 12" version of the 'New Live & Rare' EP in Italy), but more were issued from the first few reunion albums. Dance music still continues to use the format. The last Deep Purple 12" single was 'Love Conquers All' back in 1991.

Acetates.

Acetate singles are metal discs with a layer of acetate each side, into which the track is cut directly. They usually have a purple, almost black, colour and the metal might be visible at the disc edge. They were made to test the pressing in the studio or to enable musicians to hear the recording outside a studio. Acetates are very soft and wear out if played too often. Labels are usually generic record company designs, with the titles to be handwritten or typed. As acetates were cut at all stages of recording, some contain material either unreleased or different to retail releases and are very collectable. Pre Deep Purple releases on acetate are about and much prized. The most valuable acetate is probably the one cut by Deep Purple in 1968 with 'Shadows' and an instrumental version of 'Love Help Me' on, prior to them doing their first album. (both tracks now available on the Shades.. cd remaster). Most acetates are normal 7" size but they can be ten inch discs, single sided discs etc.

Vinyl 12" LP / Long Playing 33 1/3 rpm

Normal albums of around twenty minutes playing time per side, stretched much beyond that and the sound quality goes down hill. The format was launched in 1948 in America, 1950 in the UK and lasted through until around 1990 (the last Deep Purple vinyl album was 'The Battle Rages On'), although the format is still used for short runs of some new albums and reissues - the remastered 'Machine Head' was done as a 2,000 run double vinyl set. Sleeves could be single or gatefold, and contain lyric sheets or printed record bags. Other gimmicks included posters and booklets. Collectors should look for original pressings when possible, which can be determined by matrix number, the quality of the vinyl, and even the name of the printer who did the sleeve. After a few years albums were often reissued in simplified sleeves to reduce production costs. Examples include the EMI 'Fame' series which reduced In Rock and Fireball from gatefold to single sleeves.

Stereo was launched in 1958 and both mono and stereo editions of albums were issued simultaneously until the end of the sixties. Deep Purple's first album came in both formats in the UK, the mono version is very rare. As well as the main Deep Purple albums, there are compilations (an album full of tracks from other full price albums) and samplers, albums which contain a variety of different artists with maybe one or two Deep Purple tracks.

Quadraphonic LPs

Designed to give a true four channel sound when decoded using a special amplifier with four speakers, this format was launched in the early seventies but take up was slow as many people had only just gone over to stereo. It found wider acceptance in America. Quad editions are popular as they were often mixed by engineers on their own, and could contain differences in the mix, and even the music. Several Deep Purple albums were issued in quad versions in Europe and America, and even a few related titles - The James Gang albums with Tommy Bolin for example. They do usually command a higher price than regular releases, and the quad format is collected in its own right.

Promo / demo albums

These were not as widely issued as singles. Where they do exist, promotional copies usually have white labels with black text. Later on they would be normal editions but with the words 'promotional use' stamped in gold on the sleeve or on a sticker. White labels are collectable, overprinted covers aren't. One nice promo edition was for the UK 'Shades', which came in a plain card sleeve with a sticker on.

Radio Albums

These are specially assembled albums made for DJs to play. They contain either existing material or sometimes otherwise unissued sessions or live concerts. Sometimes DJ chat is included, or commercials. The most valuable are original BBC 'transcription' discs, although many have been pirated. The format was continued on CD.

Interview Discs

Usually issued as promotional devices, featuring interviews with band members and a DJ. There were some done for the first two Deep Purple reunion albums while one made for 'Rainbow Rising', with interviews, music, promo pics and a biography is highly collectable.

 

Album test pressings / white labels

These can be either pressed on acetate (see for singles) or regular vinyl but with blank labels and handwritten information on, and were done in small numbers to test new titles, or sometimes used for promotional purposes. Vinyl white labels might sometimes be issued with uncut album sleeves wrapped round. In America white labels were issued with sheets giving label and track information for review purposes. Sometimes an album would be issued as two single sided test copies.

All the above are collectable to one degree or another.

Vinyl Picture Discs

Although developed in the 1920s, the vinyl picture disc didn't really emerge in any quantity until the late seventies as a technique to boost sales to collectors. By the end of the decade many singles had an accompanying picture disc edition, often very limited (one or two of the Rainbow singles were only done in editions of 2,000). A further development was the shaped picture disc, with the normal 7" grooves pressed within a cut out shape. Picture disc albums were less widespread but still popular. Classic and reunion era Deep Purple album releases in this format exist as well as post-split titles. The actual picture was done on a printed sheet of paper, sandwiched between clear vinyl. It is not uncommon for test pressings of picture discs to be done using plain paper and some people find these collectable. Although it is tempting to frame picture discs up, as the image is on paper, they can fade or discolour in sunlight. The discs should not be purchased to play as the quality is markedly poorer than ordinary vinyl.

Colour vinyl

Again quite an old development, colour vinyl made a big comeback in the late seventies, and a number of older albums were reissued in different colours as limited editions. The French “Machine Head” is a good example. The rarest is a red vinyl issue of “Concerto” issued in Japan in early 1970. The

There are also colour vinyl 7" and 12" singles, while promo releases in colour vinyl are known - the U.S. 12" Rainbow promo of Stone Cold for example.

Box sets

A box set can take a number of formats. The idea originated in the classical world, where lengthy operas and single artist works were collected over several 78 or 33 1/3 rpm discs. Deep Purple vinyl boxes were issued with the albums in regular covers inside a cardboard box in Germany, while in Mexico there was a multi album Best Of box, where the albums came in plain paper bags inside a card box. In the CD age, box sets have taken the form of thin card slipcases holding a numbers of CDs in jewel cases, to proper card boxes holding miniature CD versions of the album sleeves, and on to major retrospectives like the Rhino and EMI sets. To remain collectable these sets need to be in their original packaging. Some dealers for example have been breaking up the EMI Singles box from 2002 and selling the discs individually.

Flexidiscs

The flexi disc originated in the fifties, when it was discovered that record grooves could be pressed onto thin clear plastic sheets. These discs were then glued to printed card backings. Advances in plastic meant stronger flexi discs could be made to play as normal singles. Because they were cheap, they were exclusively used for giveaways and promotional purposes. Most were pressed by the Lyntone company near London. The earliest example of interest to Deep Purple fans is the rare Raleigh Bikes "Bike Beat" flexi which featured a jingle performed by The Outlaws. Examples also include a magazine called Flexi Pop which carried a free Gillan flexi disc on the cover with an otherwise unissued track on. In several communist countries, flexi discs were a way of distributing Western rock music cheaply. Russian examples are known while in Poland, postcard shaped flexis with discs pressed into the centre were pressed by the hundred. They have no label, just some basic info scratched into the plastic surface. They are of curiosity value only as they are in effect pirate releases.

Bootlegs / Pirate Vinyl

(see bootleg / pirate cds)



Reel To Reel

Although blank tape and tape recording decks were popular in the UK, pre-recorded reels weren't good sellers and the format faded at the end of the sixties. In America the availability of better tape machines kept the format going right through the seventies and all Deep Purple albums (as well as many solo efforts) were issued there on this format. Reels are housed in 7" square card boxes with appropriate graphics, the tapes running at 7 1/2 ips. They make a nice collection but beware of paying over the odds on internet auction sites as they aren't especially rare or hard to find in America.

8 Track Cartridge

Developed during the sixties for in-car use primarily, the 8 track system did find some acceptance as a home format as well, mostly in America. The tape ran in a continuous loop so there was no need to turn it over to play the other side. In the UK, cartridges came with a card slipcase and collectors should stay clear of UK tapes which lack this. In America some just had the graphics on the label. Most of the Deep Purple albums were released in the 8 track format - the early only ones in America; EMI did not take up the format until later on ('Made In Europe' probably being the last).

Musicassettes / MC

Launched by Philips in 1965, the cassette remained a popular format right through into the early nineties and all Deep Purple albums were issued in this format in different territories, as well as many post split and some reunion titles. The 'Perfect Strangers' cassette featured 'Not Responsible', a track omitted from the vinyl release. The format was not popular with collectors due to poor sound quality (especially on 70s releases), limited packaging and the ease with which they became damaged. In addition running order on early releases was often moved around just to save on tape. In the early eighties some labels added bonus tracks to the cassette format in an effort to stimulate sales (for example Perfect Strangers had an extra track - Not responsible - on cassette but not on vinyl). Early cassette releases can be found at quite reasonable prices and they can make an interesting collection. The earliest usually carry the tape speed on the spine.

DCC / Digital Compact Cassette

A useful invention squashed at birth, which allowed cassettes to be manufactured digitally, thus ensuring a much better quality signal when played back on ordinary machines. Some commercial cassette were manufactured using this technology but as far as we know no Deep Purple or related titles made it.

DAT / Digital Audio Tape

A new format, which is why they didn't want DCC to take off! A smaller version of the cassette, which needed a DAT player. It recorded and played back the signal digitally to CD standard and beyond. Although available to the domestic market, it failed to take off due to the small range of available titles, and the fact that people had only just got used to CDs. I don't think any Deep Purple related titles were ever issued in this format. DAT continues to be widely used in studios for mastering and recording. ADAT is a further development which allows multi-track recordings to be made or stored for mastering.


CD / Compact Disc

Developed during the late seventies and early eighties, the CD was launched in Europe in 1984. The information on the disc was encoded digitally and needed a dedicated CD player. Initial length was 74 minutes (allegedly because this could accommodate the managing director of Sony's favourite piece of classical music), which has been pushed up towards 80. Despite often poor transfers of older material to the new format, CD was popular because the discs were less prone to damage than vinyl discs. It took a few years to become established, especially for back catalogue releases, due to the lack of packaging and the need for a player. In America the CD jewel cases were packed inside a 12" tall card box to make more of an impact at retail level but these long-boxes were eventually phased out once the format became established. As the jewel cases could only be removed by destroying the long-box, they are now quite rare. Interestingly the CD development committee did debate whether to issue CDs in 7" boxes to give the packaging more impact but this was rejected.

As CD and mastering technology improved, better reissues of earlier CDs started to appear, sometimes including extra material. So far there does not seem to be much interest in deleted editions, unless they contain material that is otherwise not available on CD. Earlier CDs also had more primitive one colour labels, usually just text. Special editions usually just take the form of revised or expanded packaging, sometimes in digi-paks. In Japan, limited editions in miniature card albums sleeves are popular and collectable, and variations of this format have been issued in Europe.

Promo CDs

Promotional editions of CDs with specially printed labels and packaging are often issued. Their collectability depends on how different from the regular release the packaging is. For example EMI promo CD of 'Fireball' just had a special label, while the promo 'Machine Head' came in an otherwise unavailable miniature version of the original gatefold sleeve. Advance promo singles with just one or two tracks on are also quite common.

3" CD singles

Developed in Japan for singles, this format was unpopular elsewhere as many CD machines couldn't play the format, even with a special adaptor. A few Deep Purple and solo singles exists in the format, including Ian Gillan's 'South Africa' single.

5" CD singles

If you thought 12" singles were a swizz, then you really loved CD singles - one or two songs on a format which could carry 75 minutes of music. For a time they carried 4-5 tracks, before marketing regulations set the maximum at three. Reunion Deep Purple CD singles are not very common and those that were issued are hard to find. It's both a retail problem - few shops stock rock singles - and an artistic one; the band can't be bothered to record new tracks for singles. CD singles often carried material unavailable elsewhere, to encourage purchase by serious fans. One Deep Purple example is 'Slow Down Sister' , only available on the 'Love Conquers All' CD & 12" single editions. As vinyl sales decreased, record companies took to issuing two versions of a single, featuring the same lead track, but different supporting tracks ( B-sides). Whitesnake's 'Too Many Tears' from 1997 is an example.

Bootlegs / pirate copies

Pirate copies are pressings which aim to mimic official pressings. Pirate vinyl versions of many Deep Purple albums were issued in less regulated areas like Asia and East Europe. Covers were either poor copies of the originals or simply made up. Pirate CDs are not uncommon, usually taking the form of cheap compilations. Numerous such Deep Purple titles have been seen. Pirate cassettes, many with their own unique track listings, are popular in Asia as well.

Bootlegs are pressings which contain material not available officially, often live recordings. The first Deep Purple bootleg LP ('H-Bomb') appeared in late 1970 and was the subject of a court case which helped make bootlegs illegal in Europe. Most such discs came in low budget sleeves and were of variable quality. The classic era bootlegs are quite collectable even though most of the music has since been issued elsewhere. By the reunion, bootlegs were much more elaborate, with double or even triple sets, often housed in full colour sleeves, though the quality of the recordings was still variable. Deep Purple suffered heavily from the practise during the eighties. It didn't take long for the first CD bootlegs to appear at the end of the decade and these eventually replaced vinyl releases. Quality again was varied and many were simply copies of older vinyl titles. Ironically the advent of recordable CDs (see below) hit the bootleg market quite hard as it was much cheaper and easier to clone discs than pay for expensive originals. CDRs with specially printed labels and even labels printed direct to disc followed.

CDR / Compact Disc Recordable

Originally the preserve of recording studios, technology to produce one-off CDs using computer technology or special dubbing machines became widely available in the late nineties. These discs are easy to spot as they usually have a blue tint to the recording surface. Although durable they can fade in strong sunlight. Many bootleggers now use this technology to produce short runs of a title, and ink-jet printers which print directly onto the CDR surface are now available.

Promo CDRs

For small runs, CDRs are now often used to provide promotional copies of new releases. These can have special labels. These are of course quite easy to forge, so collectors should avoid paying high prices for them.

Test CDs/CDRs

During the mastering stage, test CDRs are often made to check the sound quality. These can have studio labels with handwritten details, or circular paper labels generated on a laser/ink-jet printer. Test copies will usually have an A4 printed PQ sheet giving the exact timing codes for the disc. They have some collectors interest but it is as well to be careful as the technology to reproduce these sort of items is now quite widespread.

CDRW / Compact Disc Rewritable

Not a format which has much implication for the collector as they are primarily for home use.



MD / Mini Disc

A Sony digital audio format developed more for use as a portable carrier for Walkman based use. Similar to a computer floppy disc system, users can record onto the discs over and over, while commercial titles are also available (though none by Deep Purple as far as we know). The system is popular with home users as it is cheaper and easier than CDRW. However the signal is more compressed and is not popular with studios. The downloading of MP3 files to minidisc has extended the life of the format.

MP3 & Others

MP stands for Moving Pictures as the compression technology was developed to provide small video files for playing on computers. It was soon adapted and MP3 files are now used to compress audio tracks which can be downloaded from a website. The sampling rate (and therefore quality) varies. MP3 players can be used to download tracks direct from the web for replaying at home or on the move. Although of little interest to collectors, compact discs of MP3 files are being issued illegally, and one carrying all Deep Purple's albums from 68-76 in MP3 form on two discs has been seen in Russia. The sound quality is not as good as CDs but is likely to improve.

MP3 is becoming a generic name for the process. It's main competitor was Liquid Audio, which is better quality but has already been described as "the betamax of the digital audio world."

VCD / Video Compact Disc

Launched by Sony & Philips in 1993, VCD is best described as a primitive forerunner of DVD. The format only really took off in Japan & South East Asia. A plus is that playable material can easily be burnt onto CD-ROM (it uses compressed MPEG-1 video), but in general quality is VHS tape standard at best. Some DVD players can play VCD discs.

DVD / Digital Versatile Disc (more commonly referred to as Digital Video Disc)

A 5" disc digitally encoded to play back video via suitable DVD player. This format arrived in 1997 and was a development of the CD format. Variations are single layer and dual layer discs (the latter enables twice as much information to be carried and are replacing double disc sets).

Region encoding... Discs are given coding information so that they can only be played in certain areas of the world. Region 1 is USA & Canada, Region 2 is Japan & Europe, Region 3 is South East Asia, Region 4 is Australia and Central / South America, Region 5 is Eastern Europe & India, and Region 6 is China. Most music DVDs are Region 0, which means they will play on any machine. DVD machines can be chipped to play regions 1-6, and this is popular if you live in Europe and want to buy DVDs from America.

The old NTSC and PAL problem which occurred with video tapes aren't normally a concern with DVDs. DVD players bought in PAL regions can play NTSC discs, usually by converting the NTSC signal into one which modern TV sets can handle. Most NTSC players can not play PAL discs, external converter boxes generally being required. Most modern TVs in SECAM countries can read PAL signals.

At present official archive Deep Purple and related DVDs are thin on the ground due to the high cost of licensing older material. It is often cheaper to film something new.

DVD Recordable

At present there is a format war between three rival manufacturers, Philips, Panasonic and Pioneer. Philips' format is called DVD+R, Pioneer's DVD-R and Panasonic's DVD-RAM. DVD+R & DVD-R discs can be read by most DVD players (roughly 85%), while DVD-RAM can only really be played back on Panasonic DVD recorders.

If you'd like to check if your DVD player can play DVD-R discs click here to see a list, similarly to see a DVD+R compatibility list click here. For any other DVD related questions, visit the excellent Demystifying DVD FAQ list, which covers just about everything.

DVDA / Digital Versatile Disc Audio

Not until the DVD format was ready to launch did someone ponder the possibilities of using all the extra carrying capacity for purely audio use. DSD - Direct Stream Digital - was developed, to more closely follow the original wave form of the music, and thus give a sound much more akin to that of the original. The result was a huge improvement over standard CDs and the possibility of 5.1 sound, using five speakers. Two different and incompatible formats were developed. DVDA discs needs DVDA compatible players (which will also play regular DVDs) so means upgrading hardware.

SACD / Super Audio Compact Disc

The rival format offers the same sound quality but offers dual layer capability, so you can offer the listener both normal stereo sound as well as the improved 5.1 sound. Normal CD machines can play the stereo layer but a new machine is needed to play the 5.1 layer. In addition graphics, text and pictures can be included. It looks like SACD will be the dominant version, thanks in part to the ability for the discs to be copy-protected. The Concerto was the first Deep Purple disc to be issued on this format in Europe.

Blu-Ray

A blu-ray disc (abb. BD) is an advance over the DVD format. It is a high definition disc (1080 p) with a capacity five times that of a dvd. To be able to play and view blu-ray discs you need a blu-ray disc player or a Sony Play Station 3.
[Thanks to Fedor]

DualDisc

This new format emerged in 2005 as a way of overcoming the low consumer interest in (and confusion caused by) SACD and DVDA. A DualDisc has both a CD side and a DVD side, allowing artists to include (or mix) audio, video and computer content - all on one two-sided disc. It's a bit of a gimmick in that it was always possible to mix DVD and CD discs in a package together, but this way is cheaper to manufacture. The DualDisc format has been supported by all the major record labels and there are no new hardware requirements for most people. Although not everyone will be able to use all the features (e.g. for 5.1 sound you will need to have a surround sound system to make the most of it).

One side of the disc features a full-length CD audio album. The other side offers DVD content, which plays on all DVD players. This may include all or a mix of enhanced album audio, 5.1 surround sound, music videos, documentary films, lyrics and / or computer-ready digital song files. The disc also includes a DVD Launcher, which gives users access to the extras, info about new releases, additional video content, tour news, etc. In other words it gives buyers a lot more value for the money, makes buying the disc more attractive, and so helps keep the CD format going. The first Deep Purple related Dual Disc release is Ian Gillan's GILLAN'S INN. Side one has the full album in stereo, while on the other side includes a 5.1 version, a video, commentary by Ian, a version of "Smoke" which allows you to select which guitar solo you want to hear, and so on. March 2006.


Video Cassette

VHS video cassettes were split between the four main TV systems - NTSC (in America and Japan), SECAM (in France and Eastern Europe), MESECAM (Middle East) and PAL (most of Europe) - which were not compatible, although many modern PAL VCRs can play NTSC tapes. (SECAM tapes play back as monochrome on UK machines). Video cassettes are usually identified on the packaging so be careful when buying collectable videos that they are correct for your region.

The technologically superior Betamax video cassettes were launched around the same time as VHS, but this incompatible system faded out as VHS manufacturers got more titles into the market more quickly. Again NTSC and PAL titles were issued on Betamax. Sony also issued Super8 video tapes, mainly for use in digital camcorders. Philips' double-sided VCC tape format (better known as V2000) was also squeezed out of the market (there were no known Purple related releases in this format). Various older Deep Purple related releases were issued on both Beta and VHS, the first being the California Jam in 1981 (priced at £39!). There are some rarities on the format which have yet to make DVD - including releases by some of the post-split groups and titles like 'The Butterfly Ball'.

VHS itself has been made largely redundant by the launch of DVDs, especially amongst collectors and recordable DVD technology will soon replace it altogether.

CED / Capacitance Electronic Disc

Also known as Selectavision, it was manufactured by Hitachi and GEC, and launched around 1983. These were double sided 12" vinyl video discs, protected inside a plastic sheath. They were played using a sapphire stylus hidden within the machine. A few Deep Purple related items were released in the format, including Rainbow 'Live Between The Eyes' 1982.

LaserVision (Analogue)

During the late 70s there were a number of different video disc systems developed, with the Philips VLP (Video Laser Player) system the most widespread. It was released in the US first, as Discovision, and released more widely (as LaserVision) in 1982. These were 12" discs which used a special player, both sound and video were analogue. They were double sided, holding 60 minutes per side. A few Deep Purple related titles were pressed in this format including the California Jam and Rainbow's Last Pre-Reunion concert in 1984. They are nice just for the 12" packaging. The discs have been used as sources to pirate material onto DVD.

A smaller 8" disc, known as CDV was also launched in the late 1980s which usually carried one or two video tracks and a couple of audio tracks, a 'House Of Blue Light' title was issued in this format. A smaller, CD sized format (CD VIDEO) going for cross-platform compatibility was also briefly available...in 1988 the 'Bad Attitude' promo was released together with four audio tracks from 'House Of Blue Light'. The audio could be played on a conventional CD machine, the video track only in a laser disc player!

LaserDisc (Digital Sound)

After becoming obsolete by 1986, the 12" format was relaunched in the early nineties, now known as LD / 'LaserDisc'. It was still analogue video, but had digital sound. Most PAL machines could play the earlier VLP & CDV discs. It was more popular in America and Japan than Europe, but has effectively now been replaced by the generally superior quality of DVD.

 

Compiled by Simon Robinson and David Browne. Thanks to Matthew Kean & Mark Maddock.
We would appreciate comments and further suggestions for this guide.
This article is copyright Darker Than Blue 2006 and must not be copied or reproduced
without written permission from the authors.

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