Metric time is the measure of time interval using the metric system, which defines the second as the base unit of time, and multiple and submultiple units formed with metric prefixes, such as kiloseconds and milliseconds. It does not define the time of day, as this is defined by various time scales, which may be based upon the metric definition of the second. Other units of time, the minute, hour, and day, are accepted for use with the modern metric system, but are not part of it.

History[link]

When the metric system was introduced in France in 1795, it included units for length, area, dry volume, liquid capacity, weight or mass, and even currency, but not for time. Decimal time of day had been introduced in France two years earlier, but was set aside at the same time the metric system was inaugurated, and did not follow the metric pattern of a base unit and prefixed units. James Clerk Maxwell and Elihu Thomson (through the British Association for the Advancement of Science - BAAS) introduced the Centimetre gram second system of units (cgs) in 1874, in order to derive electric and magnetic metric units, following the recommendation of Carl Friedrich Gauss in 1832.

The ephemeris second (defined as 1/86400 of a mean solar day) was made one of the original base units of the modern metric system, or International System of Units (SI), at the 10th General Conference on Weights and Measures (CGPM) in 1954. The SI second was later redefined more precisely as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

Alternative units[link]

Numerous proposals have been made for alternative base units of metric time. On March 28, 1794, the president of the commission which developed the metric system, Joseph Louis Lagrange, proposed in a report to the commission the names déci-jour and centi-jour (deciday and centiday in English).^[1] Base units equivalent to decimal divisions of the day, such as 1/10, 1/100, 1/1000, or 1/100,000 day, or other divisions of the day, such as 1/20 or 1/40 day, have also been proposed, with names such as tick, meck, chi, chron, moment, etc., and multiple and submultiple units formed with metric prefixes. Such alternative units have not gained any notable acceptance, however, mostly from sheer lack of acquaintance and familiarity.

A modified second = 1/100 000 of a day = 0.864 s could be a viable alternative. Any redefinition of the second, however, creates conflicts with anything based on its precise current definition. Another unit for time, more familiar than some other suggestions, could be 14.4 minutes, i.e. a shorter quarter of an hour, or a centiday, as proposed by Lagrange. The centiday was used in China (called ke in Chinese) for thousands of years.

Another problem with metricating time is the fact that the second itself is not a decimal unit; in general, it is a sexagesimal one, defined as a sixtieth of a minute, which itself is a sixtieth of the unit above it. Minutes and seconds are seen in angular measure as well as in time, where the same conventions apply. In angular measure, it is the degree that is subdivided into minutes and seconds, while in time, it is the hour. The term "second" was never intended to define a base unit, but the SI did so anyway (the SI also did this with the kilogram, although there was less inconsistency because it was a decimal multiple, not a sexagesimal one). Adopting a metric time system would suggest that a new base unit not named a second would be more consistent with the base-10 structure of the metric system.

In the 19th century, Joseph Charles François de Rey-Pailhade proposed using the centiday, abbreviated cé, divided into 10 decicés, 100 centicés, 1000 millicés.^[2] and 10000 dimicés.^[3][4]

In 1897, the Commission de décimalisation du temps was created by the French Bureau of Longitude, with the mathematician Henri Poincaré as secretary. The commission proposed making the standard hour the base unit of metric time, but the proposal did not gain acceptance and was eventually abandoned.^[5]

Alternative meaning[link]

Metric time is sometimes used to mean decimal time. Metric time properly refers to measurement of time interval, while decimal time refers to the time of day. Standard time of day is defined by various time scales, such as UTC, which are now usually based upon the metric base unit of time, the second. Some proposals for alternative units of metric time are accompanied by decimal time scales for telling the time of day based upon these alternative units. Other proposals called "metric time" refer only to decimal time, and therefore are not truly metric.

French decimal time is sometimes called "metric time" because it was introduced around the same time as the metric system and both were decimal, but it was not part of the decree creating the original metric system and its units were named for the hour, minute and second, instead of using metric prefixes. Other decimal time standards, such as Swatch Internet Time, are not considered metric time.

In computing[link]

In computing, at least internally, metric time gained widespread use for ease of computation. Unix time gives date and time as the number of seconds since January 1, 1970, and Microsoft's FILETIME as multiples of 100ns since January 1, 1601.^[6] VAX/VMS uses the number of 100ns since November 17, 1858 and RISC OS the number of centiseconds since January 1, 1900.

None of these systems is strictly linear, as they each have discontinuities at leap seconds.

Fractions of a second[link]

While larger metric prefixes of a second are rarely used, subdivision prefixes are well established within science and technology. Milliseconds, microseconds and smaller units (but not centiseconds) are well established.

Problems[link]

The main problem of metric time lies in the units. The International System of Units has only developed prefixes regarding 10 units exponentially in both the multiple and submultiple directions. The first three multiples would be viable for use within a metric time system; they are:

However, the SI Units’ fourth value is:

This makes for relatively nonviable units with which to measure human time/life.

To make this system of prefixes work for metric time, standard units and prefixes would need to be developed or revived for the 4th and 5th exponents to make metric time viable to human life. Historically, the metric system included a myria- prefix to represent 10⁴, but the SI disposed of it. 10⁵ was represented using various ad hoc solutions; 100 000 meters composed a grade, 100 000 pascals composed a bar, and 100 000 dynes composed a newton. Meteorologists currently use a unit of 100 000 seconds (a quantity on the order of a day) to quantify atmospheric vorticity at the synoptic scale; the unit, however, does not have a name.

In popular culture[link]

Metric time appears in science fiction writing on occasion. In the novel A Deepness in the Sky by Vernor Vinge, the spacefaring Qeng Ho culture is depicted as using metric units such as the kilosecond and megasecond for all time interval measurements.

The novels Accelerando and Glasshouse by Charles Stross have several uses of metric time, including kiloseconds, megaseconds, and megayears. In the second case, humans are living in habitats circling brown dwarfs, with no lingering connection to the Solar System that gave birth to the earlier time scale. In Glasshouse characters use kiloseconds, "megs" etc. to refer to different periods of time, any earlier use of megayears has been dropped.

The Risen Empire by Scott Westerfeld uses metric time to measure time within an empire that extends over many star systems.

In television, the Simpsons episode "They Saved Lisa's Brain" has Principal Skinner saying that, thanks to the city being under Mensa's control, that the city's trains are not only running on time, but they are running on metric time, while looking at an analog clock with numbers 1–10 (which indicates decimal time).^[7]

An opening scene of Fritz Lang's 1927 film Metropolis shows a metric clock with ten numbers instead of twelve, illustrating the improved efficiency of future industrial society.

A song off of the 2000 album Veni Vidi Vicious by the Swedish band The Hives is titled "The Hives - Introduce the Metric System in Time".

See also[link]

• Decimal time
• Ke (unit)
• Swatch Internet Time

References[link]

External links[link]

• Metric unit of time (second) Official text of SI brochure from International Bureau of Weights and Measures
• Metric Time? University of Illinois Physics Department
• Decimal Time - Metric Time explains the difference between decimal time and metric time (broken link)
• c# Metric Time Open Source Project
• Metric Time clock in JavaScript

v t e Time Major concepts Time Eternity Arguments for eternity Immortality History Past Present Future Futures studies Deep time Time Portal Measurement and standards Chronometry UTC UT TAI Second Minute Hour Sidereal time Solar time Time zone Metric time Decimal time Hexadecimal time Clock Astrarium History of timekeeping devices Horology Marine chronometer Sundial Water clock Calendar Day Week Month Year Tropical year Gregorian Islamic Julian Intercalation Leap second Leap year Chronology Astronomical chronology Calendar era Chronicle Dating methodologies Geochronology Geologic Time Geological history Periodization Regnal year Timeline Religion and mythology Dreamtime Kāla Kalachakra Prophecy Time and fate deities Wheel of time Philosophy A-series and B-series B-Theory of time Causality Endurantism Eternal return Eternalism Event Perdurantism Presentism Temporal finitism Temporal parts The Unreality of Time Physical sciences Time in physics Absolute time and space Arrow of time Chronon Coordinate time Planck epoch Planck time Proper time Spacetime Theory of relativity Time dilation Gravitational time dilation Time domain T-symmetry Biology Chronobiology Circadian rhythms Psychology Mental chronometry Sense of time Specious present Sociology and anthropology Long Now Foundation Time discipline Time use research Economics Time value of money Time-based currency Time Banking Related topics Carpe diem Duration Space System time Tempus fugit Time capsule Time signature Time travel

The Edge
Background information
Birth name	David Howell Evans
Born	(1961-08-08) 8 August 1961 (age 50) Barking, Essex, England, United Kingdom
Origin	County Dublin, Ireland
Genres	Rock, post-punk, alternative rock
Occupations	Musician, songwriter, activist
Instruments	Guitar, vocals, keyboards, piano, bass guitar
Years active	1976–present
Labels	Island, Mercury
Associated acts	U2, Passengers
Website	www.u2.com
Notable instruments
Gibson Explorer Fender Stratocaster Gibson Les Paul Fender Telecaster Gretsch Country Gentleman Gretsch White Falcon Rickenbacker 330/12

David Howell Evans (born 8 August 1961), more widely known by his stage name The Edge (or just Edge),^[1] is a musician best known as the guitarist, backing vocalist, and keyboardist of the Irish rock band U2. A member of the group since its inception, he has recorded 12 studio albums with the band and has released one solo record. As a guitarist, The Edge has crafted a minimalistic and textural style of playing. His use of a rhythmic delay effect yields a distinctive ambient, chiming sound that has become a signature of U2's music.

The Edge was born in England to a Welsh family, but was raised in Ireland after moving there as an infant. In 1976, at Mount Temple Comprehensive School, he formed U2 with his fellow students and his older brother Dik. Inspired by the ethos of punk rock and its basic arrangements, the group began to write its own material. They eventually became one of the most popular acts in popular music, with successful albums such as 1987's The Joshua Tree and 1991's Achtung Baby. Over the years, The Edge has experimented with various guitar effects and introduced influences from several genres of music into his own style, including American roots music, industrial music, and alternative rock. With U2, The Edge has also played keyboards, co-produced their 1993 record Zooropa, and occasionally contributed lyrics. The Edge met his second and current wife, Morleigh Steinberg, through her collaborations with the band.

As a member of U2 and as an individual, The Edge has campaigned for human rights and philanthropic causes. He co-founded Music Rising, a charity to support musicians affected by Hurricane Katrina. He has collaborated with U2 bandmate Bono on several projects, including songs for Roy Orbison and Tina Turner, and the soundtracks to the musical Spider-Man: Turn Off the Dark and the Royal Shakespeare Company's London stage adaptation of A Clockwork Orange. In 2011, Rolling Stone magazine placed him at number 38 on its list of "The 100 Greatest Guitarists of All Time".

Personal life[link]

The Edge at a U2 concert in Anaheim (2005)

David Howell Evans was born at the Barking Maternity Hospital,^[2] Essex, England to Welsh parents Garvin and Gwenda Evans.^[1] When he was one, his family moved to County Dublin, Ireland where he attended St Andrew's National School. He received piano and guitar lessons and often performed with his brother Dik Evans before they both answered an advertisement posted by Larry Mullen, Jr. at their school, Mount Temple Comprehensive School, seeking musicians to form a band.^[3] The band accepted both of them. This band went through several incarnations before emerging as U2 in March 1978 (Dik Evans left the band just before the name change).^[3] U2 began performing in various venues in Ireland and eventually began developing a following. Their debut album, Boy, was released in 1980.

In 1981, leading up to the October tour, Evans came very close to leaving U2 for religious reasons, but he decided to stay.^[3] During this period, he became involved with a group called Shalom Tigers, in which bandmates Bono and Larry Mullen Jr. were also involved.^[4] Shortly after deciding to remain with the band, he wrote a piece of music that later became "Sunday Bloody Sunday".^[3] The Edge married his high school girlfriend Aislinn O'Sullivan on 12 July 1983.^[5] The couple had three daughters together: Hollie in 1984, Arran in 1985 and Blue Angel in 1989.^[4] The couple separated in 1990, but were unable to get officially divorced because of Irish laws regarding marriage annulment; divorce was legalised in 1995 and the couple were legally divorced in 1996.^[4]

In 1993, The Edge began dating Morleigh Steinberg, a professional dancer and choreographer employed by the band as a belly dancer during the Zoo TV Tour. They had a daughter, Sian (born 1997), and a son, Levi (born 25 October 1999),^[4] before marrying on 22 June 2002.^[4] He appeared in the 2009 music documentary film It Might Get Loud.^[6] The Edge has been criticized for his efforts to build five luxury mansions on a 156 acre plot of land in Malibu, California.^[7] The California Coastal Commission voted 8-4 against the plans, with the project described by the commission's executive director, Peter Douglas, as "In 38 years...one of the three worst projects that I've seen in terms of environmental devastation...It's a contradiction in terms – you can't be serious about being an environmentalist and pick this location."^[7] The Santa Monica Mountains Conservancy agreed to remain neutral on the issue following a $1 million donation from The Edge and a commitment from The Edge to designate 100 acres of the land as open space for public footpaths.^[7]

Music style[link]

Guitar playing[link]

As a guitar player, The Edge has a sound typified by a low-key playing style, a chiming, shimmering sound (thanks in part to the sound of VOX AC-30s) that he achieves with extensive use of delay effects and reverb. The feedback delay is often set to a dotted eighth note (3/16 of a measure), and the feedback gain is adjusted until a note played repeats two or three times.^{[citation needed]}

On 1987's The Joshua Tree, The Edge often contributes just a few simple lead lines given depth and richness by an ever-present delay. For example, the introduction to "Where the Streets Have No Name" is simply a repeated six-note arpeggio, broadened by a modulated delay effect. The Edge has said that he views musical notes as "expensive", in that he prefers to play as few notes as possible. He said in 1982 of his style,

"I like a nice ringing sound on guitar, and most of my chords I find two strings and make them ring the same note, so it's almost like a 12-string sound. So for E I might play a B, E, E and B and make it ring. It works very well with the Gibson Explorer. It's funny because the bass end of the Explorer was so awful that I used to stay away from the low strings, and a lot of the chords I played were very trebly, on the first four, or even three strings. I discovered that through using this one area of the fretboard I was developing a very stylized way of doing something that someone else would play in a normal way."^[9]

Many different influences have shaped The Edge's guitar technique.^{[citation needed]} His first guitar was an old acoustic guitar that his mother bought him at a local flea market for only a few pounds; he was nine at the time. He and his brother Dik Evans both experimented with this instrument.^[9] He said in 1982 of this early experimentation, "I suppose the first link in the chain was a visit to the local jumble sale where I purchased a guitar for a pound. That was my first instrument. It was an acoustic guitar and me and my elder brother Dik both played it, plonking away, all very rudimentary stuff, open chords and all that."^[9] The Edge has stated that many of his guitar parts are based around guitar effects. This is especially true from the Achtung Baby era onwards, although much of the band's 1980s material made heavy use of echos.

Vocals[link]

The Edge in June 2005

The Edge also supplies the backing vocals for U2. U2's 1983 live album and video release, Under a Blood Red Sky and Live at Red Rocks: Under a Blood Red Sky are good reference points for his singing (as are the live DVDs from the Elevation Tour, U2 Go Home: Live from Slane Castle and Elevation 2001: Live from Boston). For example, he sings the chorus to "Sunday Bloody Sunday" (Bono harmonizes on the final 'Sunday'). U2 used this tradeoff technique later in "Bullet the Blue Sky" as well. His backing vocals are sometimes in the form of a repeated cry; examples of songs that use this approach include "Beautiful Day", "New Year's Day" and "Stay (Faraway, So Close!)". Another technique he uses in his backing vocals is the falsetto, in songs such as "Stuck in a Moment You Can't Get Out Of", "Sometimes You Can't Make It on Your Own", "A Man and a Woman", "The Wanderer", live versions of "The Fly", and "Window in the Skies".

The Edge sings the lead vocal on "Van Diemen's Land" and "Numb", the first half of the song "Seconds", dual vocals with Bono in "Discotheque", and the bridge in the song "Miracle Drug".^[4] He also sings the occasional lead vocal in live renditions of other songs (such as "Sunday Bloody Sunday" during the PopMart Tour and "Party Girl" during the Rotterdam Zoo TV show when it was Bono's birthday).^[10] He also plays a solo acoustic version of the song "Love is Blindness" that is featured in the documentary film From the Sky Down.

Other instruments[link]

He has played piano and keyboards on many of the band's songs, including "I Fall Down", "October", "So Cruel", "New Year's Day", "Running to Stand Still", "Miss Sarajevo", "The Hands that Built America", and "Original of the Species" and others. He plays the organ on "Please". In live versions of "New Year's Day", "The Unforgettable Fire", "Your Blue Room", and "Moment of Surrender", he plays both the piano and guitar parts alternately. In most live versions of "Original of the Species," piano is the only instrument played during the song. Although The Edge is the band's lead guitarist, he occasionally plays bass guitar, including the live performances of the song "40" where The Edge and bassist Adam Clayton switch instruments.

Solo recordings[link]

In addition to his regular role within U2, The Edge has also recorded with such artists as Johnny Cash, B. B. King, Tina Turner, Ronnie Wood, Jay-Z, and Rihanna. The Edge connected with Brian Eno and Lanois collaborator Michael Brook (the creator of the infinite guitar, which he regularly uses), working with him on the score to the film Captive (1986). From this soundtrack the song "Heroine", the vocal of which was sung by a young Sinéad O'Connor was released as a single.

He also created the theme song for season one and two of The Batman. He and fellow U2 member, Bono, wrote the lyrics to the theme of the 1995 James Bond film GoldenEye. The Edge, along with bandmate Bono, recently composed a musical adaptation of Spider-Man. On May 25, 2011, a single titled Rise Above 1: Reeve Carney Featuring Bono and The Edge was released digitally.^[11] The music video was released on July 28, 2011.^[12]

Musical equipment[link]

Edge's 1964 Vox AC30 on stage in Foxborough for the U2 360° Tour.

The Edge plays electric guitar, acoustic guitar, keyboards, piano, bass guitar (on "40" and "Race Against Time") and lap steel guitar. Compared to many lead guitarists, The Edge is known for using many more guitars during a show. According to his guitar tech Dallas Schoo, a typical lead guitarist uses four or five different guitars in one night, whereas The Edge takes 45 on the road, and uses 17 to 19 in one 2.5-hour concert. He is estimated to have more than 200 guitars in the studio.^{[citation needed]}

Philanthropy[link]

In 2005, The Edge along with Bob Ezrin and Henry Juszkiewicz co-founded Music Rising, a charity that helped provide replacement instruments for those that were lost in Hurricane Katrina. The instruments were originally only replaced for professional musicians but they soon realized the community churches and schools needed instruments as well. The charity's slogan is "Rebuilding the Gulf Region note by note" and has so far helped over a hundred musicians who were affected by Hurricane Katrina. The Edge also serves on the board of the Angiogenesis Foundation, a 501(c)(3) nonprofit organization dedicated to improving global health by advancing angiogenesis-based medicine, diets, and lifestyle.^[13]

See also[link]

• Timeline of U2
• List of people on stamps of Ireland

References[link]

Footnotes

Bibliography

External links[link]

This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive or inappropriate external links, and converting useful links where appropriate into footnote references. (October 2011)

Wikimedia Commons has media related to: The Edge

Wikiquote has a collection of quotations related to: The Edge

• U2.com, official U2 site
• Music Rising
• The Edge at the Internet Movie Database
• The Edge – Album Credits
• A Study of The Edge's Guitar Delay
• The Edge: 'It's all about the vision'
• Food Bank For New York City public service announcement
• Comment on the mathematical analysis of The Edge's guitar sound

A black sheep stands out from the flock

The Black Sheep, from a 1901 edition of Mother Goose by William Wallace Denslow.

A black sheep (Hebridean)

In the English language, black sheep is an idiom used to describe an odd or disreputable member of a group, especially within a family. The term has typically been given negative implications, implying waywardness.^[1] It derived from the atypical and unwanted presence of other black individuals in flocks of white sheep.

In psychology, the black sheep effect refers to the tendency of group members to judge likeable ingroup members more positively and deviant ingroup member more negatively than comparable outgroup members.^[2]

Idiomatic usage[link]

The term originated from the occasional black sheep which are born into a flock of white sheep due to a genetic process of recessive traits. Black wool was considered commercially undesirable because it could not be dyed.^[1] In 18th and 19th century England, the black color of the sheep was seen as the mark of the devil.^[3] In modern usage, the expression has lost some of its negative connotations, though the term is usually given to the member of a group who has certain characteristics or lack thereof deemed undesirable by that group.^[4]

The idiom is also found in other languages, e.g., French, Serbian, Bulgarian, Hebrew, Portuguese, Bosnian, Greek, Turkish, Dutch, Afrikaans, Swedish, Danish, Spanish, Czech, Slovak, Romanian and Polish. The same concept is illustrated in some other languages by the phrase "white crow": for example belaya vorona (белая ворона) in Russian and kalag-e sefid (کلاغ سفید) in Persian. A variant form of black sheep, "the red sheep of the family", was used by Jessica Mitford to describe herself, a communist in a family of aristocratic fascists.^[5]

Biological origin[link]

In sheep, a white fleece is not albinism but a dominant gene that actively switches color production off, thus obscuring any other color that may be present.^{[citation needed]} As a result, a black fleece in most sheep is recessive, so if a white ram and a white ewe are each heterozygous for black, in about 25% of cases they will produce a black lamb. In fact in most white sheep breeds only a few white sheep are heterozygous for black, so black lambs are usually much rarer than this. Some breeds of sheep (such as the Hebridean, Ouessant, Black Welsh Mountain and Karakul) are normally black.

Black sheep effect (Psychology)[link]

Overview[link]

In 1988, Marques, Yzerbyt and Leyens^[2] conducted an experiment where Belgian students rated the following groups according to trait-descriptors (e.g., sociable, polite, violent, cold): unlikeable Belgian students, unlikeable North African students, likeable Belgian students, and likeable North African students. The results provided support that the favourability is the highest for likeable ingroup members and the lowest for unlikeable ingroup members, whereas the favourability of unlikeable and likeable outgroup members is between the both former ones. These extreme judgements of likeable and unlikeable (i.e., deviant) ingroup members, relatively to comparable outgroup members is called “black sheep effect”. This effect has been shown in various intergroup contexts and under a variety of conditions, and in many experiments manipulating likeability and norm deviance (e.g., Branscombe, Wann, Noel, & Coleman, 1993;^[6] Coull, Yzerbyt, Castano, Paladino, & Leemans, 2001;^[7] Khan & Lambert, 1998;^[8] Pinto, Marques, Levine, & Abrams, 2010).^[9]

Explanations[link]

A prominent explanation of the black sheep effect derives from the social identity approach (see social identity theory, Tajfel & Turner, 1979;^[10] and self-categorization theory, Turner, Hogg, Oakes, Reicher, & Wetherell, 1987).^[11] Group members are motivated to sustain a positive and distinctice social identity and, as a consequence, group members emphasize likeable members and evaluate them more positve than outgroup members, bolstering the positive image of their ingroup (see ingroup bias). Furthermore, the positive social identity may be threatened by group members who deviate from a relevant group norm. To protect the positive group image, ingroup members derogate ingroup deviants more harshly than deviants of an outgroup (Marques, Abrams, Páez, & Hogg, 2001).^[12] In addition, Eidelman and Biernat (2003)^[13] have shown that personal identities are also threatened through deviant ingroup members. They argue that devaluation of deviant members is an individual response of interpersonal differentiation. Khan and Lambert (1998)^[8] suggest that cognitive processes like assimilation and contrast, which may underline the effect, should be examined.

Limitations[link]

Even though there is widely support for the black sheep effect, the opposite pattern has been found, for example, that White participants judge unqualified Black targets more negative than comparable White targets (e.g., Feldman, 1972;^[14] Linville & Jones, 1980).^[15] Consequentely, there are several factors which influence the black sheep effect. For instance, the higher the identification with the ingroup, and the higher the entitativity of the ingroup, the more the black sheep effect emerges (e.g., Castano, Paladino, Coull, & Yzerbyt, 2002;^[16] Lewis & Sherman, 2010).^[17] Even situational factors explaining the deviance have an influence whether the black sheep effect occurs (De Cremer & Vanbeselaere, 1999).^[18]

See also[link]

Look up black sheep in Wiktionary, the free dictionary.

• Black swan theory
• Glossary of sheep husbandry: see entry for "black wool".
• Scapegoat
• The Ugly Duckling

References[link]

External links[link]

• Exploration of the etymology of the phrase "black sheep of the family"
• "The black sheep effect: Judgmental extremity towards ingroup members in inter-and intra-group situations". European Journal of Social Psychology (Science Direct) 18 (3): 287–292. DOI:10.1002/ejsp.2420180308. http://www.sciencedirect.com/science/journal/00221031. Retrieved 2008-01-04.