Digamma
Encyclopedia
Digamma is an archaic letter of the Greek alphabet
Greek alphabet
The Greek alphabet is the script that has been used to write the Greek language since at least 730 BC . The alphabet in its classical and modern form consists of 24 letters ordered in sequence from alpha to omega...

 which originally stood for the sound /w/ and later remained in use only as a numeral symbol
Greek numerals
Greek numerals are a system of representing numbers using letters of the Greek alphabet. They are also known by the names Ionian numerals, Milesian numerals , Alexandrian numerals, or alphabetic numerals...

 for the number "6". Whereas it was originally called wau, its most common appellation in classical Greek is digamma, while in its numeral function it was called episēmon during the Byzantine era. Today the numeral sign is often called stigma, after the value of a Byzantine Greek ligature σ-τ (ϛ), which shares the same shape and was used as a textual ligature in Greek print until the 19th century.

Digamma/wau was part of the original archaic Greek alphabet as initially adopted from Phoenician
Phoenician alphabet
The Phoenician alphabet, called by convention the Proto-Canaanite alphabet for inscriptions older than around 1050 BC, was a non-pictographic consonantal alphabet, or abjad. It was used for the writing of Phoenician, a Northern Semitic language, used by the civilization of Phoenicia...

. Like its model, Phoenician waw
Waw (letter)
Waw is the sixth letter of the Northwest Semitic family of scripts, including Phoenician, Aramaic, Hebrew, Syriac, and Arabic ....

, it represented the voiced labial-velar approximant
Voiced labial-velar approximant
The voiced labiovelar approximant is a type of consonantal sound, used in certain spoken languages, including English. It is the sound denoted by the letter "w" in the English alphabet; likewise, the symbol in the International Phonetic Alphabet that represents this sound is , and the equivalent...

 /w/ and stood in the 6th position in the alphabet, between epsilon
Epsilon
Epsilon is the fifth letter of the Greek alphabet, corresponding phonetically to a close-mid front unrounded vowel . In the system of Greek numerals it has a value of 5. It was derived from the Phoenician letter He...

 and zeta
Zeta
-Science:* Zeta functions, in mathematics** Riemann zeta function* Zeta potential, the electrokinetic potential of a colloidal system* Tropical Storm Zeta , formed in December 2005 and lasting through January 2006* Z-pinch, in fusion power...

. It is the consonantal doublet of the vowel letter upsilon
Upsilon
Upsilon is the 20th letter of the Greek alphabet.  In the system of Greek numerals it has a value of 400. It is derived from the Phoenician waw. The name of the letter is pronounced in Modern Greek, and in English , , or...

 (/u/), which was also derived from waw but was placed at the end of the Greek alphabet. Digamma/wau is in turn the ancestor of the Roman letter F. As an alphabetic letter it is attested in archaic and dialectal ancient Greek inscriptions until the classical period.

The shape of the letter went through a development from through , , , to or , which at that point was conflated with the σ-τ ligature . In modern print, a distinction is made between the letter in its original alphabetic role as a consonant sign, which is rendered as "Ϝ" or its modern lowercase variant "ϝ", and the numeric symbol, which is represented by "ϛ" (or, in modern practice in Greece, replaced with "στ").

Mycenaean Greek

The sound /w/ existed in Mycenean Greek, as attested in Linear B
Linear B
Linear B is a syllabic script that was used for writing Mycenaean Greek, an early form of Greek. It pre-dated the Greek alphabet by several centuries and seems to have died out with the fall of Mycenaean civilization...

 and archaic Greek inscriptions using digamma.  It is also confirmed by the Hittite
Hittite language
Hittite is the extinct language once spoken by the Hittites, a people who created an empire centred on Hattusa in north-central Anatolia...

 name of Troy
Troy
Troy was a city, both factual and legendary, located in northwest Anatolia in what is now Turkey, southeast of the Dardanelles and beside Mount Ida...

, Wilusa, corresponding to the Greek name *Wilion.

Classical Greek

The /w/ sound was lost at various times in various dialects, mostly before the classical period. 

In Ionic
Ionic Greek
Ionic Greek was a subdialect of the Attic–Ionic dialect group of Ancient Greek .-History:Ionic dialect appears to have spread originally from the Greek mainland across the Aegean at the time of the Dorian invasions, around the 11th Century B.C.By the end of the Greek Dark Ages in the 5th Century...

, /w/ had probably disappeared before Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

's epics were written down (7th century BC), but its former presence can be detected in many cases because its omission left the meter
Meter (poetry)
In poetry, metre is the basic rhythmic structure of a verse or lines in verse. Many traditional verse forms prescribe a specific verse metre, or a certain set of metres alternating in a particular order. The study of metres and forms of versification is known as prosody...

 defective. For example, the words (king), found in the Iliad
Iliad
The Iliad is an epic poem in dactylic hexameters, traditionally attributed to Homer. Set during the Trojan War, the ten-year siege of the city of Troy by a coalition of Greek states, it tells of the battles and events during the weeks of a quarrel between King Agamemnon and the warrior Achilles...

, which would originally have been /wánaks/, and (wine) are sometimes used in the meter where a word starting with a consonant would be expected. Further evidence coupled with cognate-analysis shows that was earlier /wóînos/ (cf. Cretan Doric
Doric Greek
Doric or Dorian was a dialect of ancient Greek. Its variants were spoken in the southern and eastern Peloponnese, Crete, Rhodes, some islands in the southern Aegean Sea, some cities on the coasts of Asia Minor, Southern Italy, Sicily, Epirus and Macedon. Together with Northwest Greek, it forms the...

 ibêna, cf. Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 vīnum and English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 "wine").

Aeolian was the dialect that kept the sound /w/ longest. In discussions by ancient Greek grammarians of the Hellenistic era, the letter is therefore often described as a characteristic Aeolian feature.

For some time, word-initial /w-/ remained foreign to Greek phonology, and was dropped in loanwords, compare the name of Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 (Italia from Oscan Viteliu *Ϝιτελιυ) or of the Veneti
Adriatic Veneti
The Veneti were an ancient people who inhabited north-eastern Italy, in an area corresponding to the modern-day region of the Veneto....

 (Greek Ἐνετοί - Enetoi). By the 2nd century BC, the phoneme was once again registered, compare for example the spelling of for vates
Vates
The earliest Latin writers used vātēs to denote "prophets" and soothsayers in general; the word fell into disuse in Latin until it was revived by Virgil...

.

Pamphylian digamma

In some local (epichoric) alphabets, a variant glyph of the letter digamma existed that resembled modern Cyrillic И. In one local alphabet, that of Pamphylia
Pamphylia
In ancient geography, Pamphylia was the region in the south of Asia Minor, between Lycia and Cilicia, extending from the Mediterranean to Mount Taurus . It was bounded on the north by Pisidia and was therefore a country of small extent, having a coast-line of only about 75 miles with a breadth of...

, this variant form existed side by side with standard digamma as two distinct letters. It has been surmised that in this dialect the sound /w/ may have changed to labiodental /v/ in some environments. The F-shaped letter may have stood for the new /v/ sound, while the special И-shaped form signified those positions where the old /w/ sound was preserved.

Numeral

Digamma/wau remained in use in the system of Greek numerals
Greek numerals
Greek numerals are a system of representing numbers using letters of the Greek alphabet. They are also known by the names Ionian numerals, Milesian numerals , Alexandrian numerals, or alphabetic numerals...

 attributed to Miletus
Miletus
Miletus was an ancient Greek city on the western coast of Anatolia , near the mouth of the Maeander River in ancient Caria...

, where it stood for the number 6, reflecting its original place in the sequence of the alphabet. It was one of three letters that were kept in this way in addition to the 24 letters of the classical alphabet, the other two being koppa (ϙ) for 90, and sampi
Sampi
Sampi is an archaic letter of the Greek alphabet. It was used in addition to the classical 24 letters of the alphabet to denote some type of a sibilant sound, probably or , in some eastern Ionic dialects of ancient Greek in the 6th and 5th centuries BC...

 (ϡ) for 900. During their history in handwriting in late antiquity and the Byzantine era, all three of these symbols underwent several changes in shape, with digamma ultimately taking the form of "ϛ". It has remained in use as a numeral in Greek to the present day, in contexts such as enumerating chapters in a book or other items in a set.

Glyph development

Epigraphy

Digamma was derived from Phoenician waw, which was shaped roughly like an Y (). Of the two Greek reflexes of waw, digamma retained the alphabetic position, but had its shape modified to , while the upsilon
Upsilon
Upsilon is the 20th letter of the Greek alphabet.  In the system of Greek numerals it has a value of 400. It is derived from the Phoenician waw. The name of the letter is pronounced in Modern Greek, and in English , , or...

 retained the original shape but was placed in a new alphabetic position. Early Crete had an archaic form of digamma somewhat closer to the original Phoenician, , or a variant with the stem bent sidewards . The shape , during the archaic period, underwent a development parallel to that of epsilon
Epsilon
Epsilon is the fifth letter of the Greek alphabet, corresponding phonetically to a close-mid front unrounded vowel . In the system of Greek numerals it has a value of 5. It was derived from the Phoenician letter He...

 (which changed from to "E", with the arms becoming orthogonal and the lower end of the stem being shed off). For digamma, this led to the two main variants of classical "F" and square .

The latter of these two shapes became dominant when used as a numeral, with "F" only very rarely employed in this function. However, in Athens, both of these were avoided in favour of a number of alternative numeral shapes .

Early handwriting

In cursive handwriting, the square-C form developed further into a rounded form resembling a "C" (found in papyrus manuscripts as , on coins sometimes as ). It then developed a downward tail at the end and finally adopted a shape like a Latin "s" These cursive forms are also found in stone inscriptions in late antiquity.

Conflation with the στ ligature

In the ninth and tenth centuries, the cursive shape digamma was visually conflated with a ligature
Ligature (typography)
In writing and typography, a ligature occurs where two or more graphemes are joined as a single glyph. Ligatures usually replace consecutive characters sharing common components and are part of a more general class of glyphs called "contextual forms", where the specific shape of a letter depends on...

 of sigma
Sigma
Sigma is the eighteenth letter of the Greek alphabet, and carries the 'S' sound. In the system of Greek numerals it has a value of 200. When used at the end of a word, and the word is not all upper case, the final form is used, e.g...

 (in its historical "lunate" form) and tau
Tau
Tau is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.The name in English is pronounced , but in modern Greek it is...

 ( + = ). The στ-ligature had became common in minuscule
Minuscule Greek
The minuscule script was a writing style in the history of Greek writing which was used as a book hand in Byzantine manuscripts since the 9th and 10th centuries. It replaced the earlier style of uncial writing, from which it differed in using smaller, more rounded and more connected letter forms,...

 handwriting from the 9th century onwards. Both closed and open forms were subsequently used without distinction both for the ligature and for the numeral. The ligature took on the name of "stigma" or "sti", and the name stigma is today applied to it both in its textual and in the numeral function. The association between its two functions as a numeral and as a sign for "st" became so strong that in modern typographic practice in Greece, whenever the ϛʹ sign itself is not available, the letter sequences στʹ or ΣΤʹ are used instead for the number 6.

Typography

In western typesetting during the modern era, the numeral symbol was routinely represented by the same character as the stigma ligature (ϛ). In normal text, this ligature together with numerous others continued to be used widely until the early nineteenth century, following the style of earlier minuscule handwriting, but ligatures then gradually dropped out of use. The stigma ligature was among those that survived longest, but it too became obsolete in print after the mid-19th century. Today it is used only to represent the numeric digamma, and never to represent the sequence στ in text.

Along with the other special numeric symbols koppa and sampi, numeric digamma/stigma normally has no distinction between uppercase and lowercase forms, (while other alphabetic letters can be used as numerals in both cases). Distinct uppercase versions were occasionally used in the 19th century. Several different shapes of uppercase stigma can be found, with the lower end either styled as a small curved S-like hook , or as a straight stem, the latter either with a serif or without one . An alternative uppercase stylization in some twentieth-century fonts is , visually a ligature of Roman-style uppercase C and T.

The characters used for numeric digamma/stigma are distinguished in modern print from the character used to represent the ancient alphabetic digamma, the letter for the [w] sound. This is rendered in print by a Latin "F", or sometimes a variant of it specially designed to fit in typographically with Greek (Ϝ). It has a modern lowercase form (ϝ) that typically differs from Latin "f" by having two parallel horizontal strokes like the uppercase character, with the vertical stem often being somewhat slanted to the right or curved, and usually descending below the baseline
Baseline (typography)
In European and West Asian typography and penmanship, the baseline is the line upon which most letters "sit" and below which descenders extend.In the example to the right, the letter 'p' has a descender; the other letters sit on the baseline....

. This character is used in Greek epigraphy
Epigraphy
Epigraphy Epigraphy Epigraphy (from the , literally "on-writing", is the study of inscriptions or epigraphs as writing; that is, the science of identifying the graphemes and of classifying their use as to cultural context and date, elucidating their meaning and assessing what conclusions can be...

 to transcribe the text of ancient inscriptions that contain "Ϝ", and in linguistics and historical grammar when describing reconstructed proto-forms of Greek words that contained the sound /w/.

Glyph confusion

Throughout much of its history, the shape of digamma/stigma has often been very similar to that of other symbols, with which it can easily be confused. In ancient papyri, the cursive C-shaped form of numeric digamma is often indistinguishable from the C-shaped ("lunate") form that was then the common form of sigma
Sigma
Sigma is the eighteenth letter of the Greek alphabet, and carries the 'S' sound. In the system of Greek numerals it has a value of 200. When used at the end of a word, and the word is not all upper case, the final form is used, e.g...

. The same similarity is still found today, since both the modern stigma (ϛ) and modern final sigma (ς) look identical or almost identical in most fonts; both are historically continuations of their ancient C-shaped forms with the addition of the same downward flourish. If the two characters are distinguished in print, the top loop of stigma tends to be somewhat larger and to extend farther to the right than that of final sigma. The two characters are, however, always distinguishable from the context in modern usage, both in numeric notation and in text: the final form of sigma never occurs in numerals (the number 200 being always written with the medial sigma, σ), and in normal Greek text the sequence "στ" can never occur word-finally.

The medieval s-like shape of digamma has the same shape as a contemporary abbreviation for ("and").

Yet another case of glyph confusion exists in the printed uppercase forms, this time between stigma and the other numeral, koppa
Koppa
Koppa is an archaic letter-like numeral character of the Cyrillic writing system. Its form are derived from the Greek letter Koppa ....

 (90). In ancient and medieval handriting, koppa developed from through , , to . The uppercase forms and can represent either koppa or stigma. Frequent confusion between these two values in contemporary printing was already noted by some commentators in the eighteenth century. The ambiguity continues in modern fonts, many of which continue to have glyph similar to for either koppa or stigma.

Names

The symbol has been called by a variety of different names, referring either to its alphabetic or its numeral function or both.

Wau

Wau (variously rendered as vau, waw or similarly in English) is the original name of the alphabetic letter for /w/ in ancient Greek. It is often cited in its reconstructed acrophonic spelling "". This form itself is not historically attested in Greek inscriptions, but the existence of the name can be inferred from descriptions by contemporary Latin grammarians, who render it as vav. In later Greek, where both the letter and the sound it represented had become inaccessible, the name is rendered as or . In the 19th century, the anglicized form vau was a common name for the symbol ϛ in its numerical function, used by authors who distinguished it both from the alphabetic "digamma" and from ϛ as a στ ligature.

Digamma

The name digamma was used in ancient Greek and is the most common name for the letter in its alphabetic function today. It literally means "double gamma" and is descriptive of the original letter's shape.

Episemon

The name episēmon was used for the numeral symbol during the Byzantine era and is still sometimes used today, either as a name specifically for digamma/stigma, or as a generic term for the whole group of extra-alphabetic numeral signs (digamma, koppa
Koppa
Koppa is an archaic letter-like numeral character of the Cyrillic writing system. Its form are derived from the Greek letter Koppa ....

 and sampi
Sampi
Sampi is an archaic letter of the Greek alphabet. It was used in addition to the classical 24 letters of the alphabet to denote some type of a sibilant sound, probably or , in some eastern Ionic dialects of ancient Greek in the 6th and 5th centuries BC...

). The Greek word "", from (epi-, "on") and (sēma, "sign"), literally means "a distinguishing mark", "a badge", but is also the neuter form of the related adjective "" ("distinguished", "remarkable"). This word was connected to the number "six" through early Christian mystical numerology
Numerology
Numerology is any study of the purported mystical relationship between a count or measurement and life. It has many systems and traditions and beliefs...

. According to an account of the teachings of the heretic Marcus
Marcus (Marcosian)
Marcus was the founder of the Marcosian Gnostic sect in the 2nd century AD. He was a disciple of Valentinus, with whom his system mainly agrees. His doctrines are almost exclusively known to us through a long polemic in Adversus Haereses, in which Irenaeus gives an account of his teaching and his...

 given by the church father Irenaeus
Irenaeus
Saint Irenaeus , was Bishop of Lugdunum in Gaul, then a part of the Roman Empire . He was an early church father and apologist, and his writings were formative in the early development of Christian theology...

, the number six was regarded as a symbol of Christ, and was hence called "" ("the outstanding number"); likewise, the name (Jesus), having six letters, was "" ("the outstanding name"), and so on. The sixth-century treatise About the Mystery of the Letters
About the Mystery of the Letters
About the Mystery of the Letters is an anonymous Christian treatise containing a mystical doctrine about the names and forms of the Greek and Hebrew letters...

, which also links the six to Christ, calls the number sign to Episēmon throughout. The same name is still found in a fifteenth-century arithmetical manual by the Greek mathematician Nikolaos Rabdas. It is also found in a number of western European accounts of the Greek alphabet written in Latin during the early Middle Ages. One of them is the work De loquela per gestum digitorum, a didactic text about arithmetics attributed to the Venerable Bede, where the three Greek numerals for 6, 90 and 900 are called "episimon", "cophe" and "enneacosis" respectively. From Beda, the term was adopted by the seventeenth century humanist
Renaissance humanism
Renaissance humanism was an activity of cultural and educational reform engaged by scholars, writers, and civic leaders who are today known as Renaissance humanists. It developed during the fourteenth and the beginning of the fifteenth centuries, and was a response to the challenge of Mediæval...

 Joseph Justus Scaliger
Joseph Justus Scaliger
Joseph Justus Scaliger was a French religious leader and scholar, known for expanding the notion of classical history from Greek and Ancient Roman history to include Persian, Babylonian, Jewish and Ancient Egyptian history.-Early life:He was born at Agen, the tenth child and third son of Italian...

. However, misinterpreting Beda's reference, Scaliger applied the term episēmon not as a name proper for digamma/6 alone, but as a cover term for all three numeral letters. From Scaliger, the term found its way into modern academic usage in this new meaning, of referring to complementary numeral symbols standing outside the alphabetic sequence proper, in Greek and other similar scripts.

Gabex or Gamex

In one remark in the context of a biblical commentary, the 4th century scholar Ammonius of Alexandria
Ammonius of Alexandria (Christian)
Ammonius of Alexandria was a Christian philosopher who lived in the 3rd century. He is not to be confused with Ammonius Saccas, the Neoplatonist philosopher, also from Alexandria....

 is reported to have mentioned that the numeral symbol for 6 was called gabex by his contemporaries. The same reference in Ammonius has alternatively been read as gam(m)ex by some modern authors. Ammonius as well as later theologians discuss the symbol in the context of explaining the apparent contradiction and variant readings between the gospels in assigning the death of Jesus either to the "third hour" or "sixth hour", arguing that the one numeral symbol could easily have been substituted for the other through a scribal error.

Stigma

The name "stigma" was originally a common Greek noun meaning "a mark, dot, puncture" or generally "a sign", from the verb στίζω ("to puncture"). It had an earlier writing-related special meaning, being the name for a dot as a punctuation mark, used for instance to mark shortness of a syllable in the notation of rhythm. It was then co-opted as a name specifically for the στ ligature, evidently because of the acrophonic
Acrophony
Acrophony is the naming of letters of an alphabetic writing system so that a letter's name begins with the letter itself. For example, Greek letter names are acrophonic: the names of the letters α, β, γ, δ, are spelled with the respective letters: ....

 value of its initial st- as well as the analogy with the name of sigma. Other names coined according to the same analogical principle are sti or stau.

Computer encoding

In Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

, the sign for the numeral digamma/stigma is present in an uppercase and lowercase version, at U+03DA (Ϛ, "Greek letter stigma") and U+03DB (ϛ, "Greek small letter stigma") respectively. The uppercase letter was present in the standard from version 1.3 (1993), whereas the lowercase equivalent was only added in version 3.0 (1999).
(Hence, while the uppercase character may show great differences in shape between different fonts, the lowercase character may be lacking in some older fonts.)

Alphabetic digamma (wau) is present as uppercase U+03DC (Ϝ) and lowercase U+03DD (ϝ). In July 2006, another pair of uppercase and lowercase digamma with bold typeface were added to the Unicode standard version 5.0, at code points U+1D7CA and U+1D7CB. Their intended use is as mathematical symbols, not regular text.

The И-shaped "Pamphylian digamma" was encoded in Unicode version 5.1 and has code U+0376 (uppercase) and U+0377 (lowercase) ( ). The same codepoints are shared with the identical-looking but historically different Arcadian "Tsan". As of 2010, these new characters are not yet supported by most fonts. As these characters have no tradition of typographic representation in mixed-case modern print, new designs for the lowercase letter were created only for Unicode.

A clone of the numeral ϛ for use in Coptic
Coptic alphabet
The Coptic alphabet is the script used for writing the Coptic language. The repertoire of glyphs is based on the Greek alphabet augmented by letters borrowed from the Demotic and is the first alphabetic script used for the Egyptian language...

 has been encoded separately, since Unicode version 4.1, at U+2C8A ("Coptic capital letter sou", Ⲋ) and U+2C85 ("Coptic small lstter sou", ⲋ). There are also codepoints for an F-shaped sign used as a musical notation symbol in ancient Greek vocal music (U+1D213, "Greek vocal notation symbol-20"), and for a small subscript ϛ-shaped symbol for use in Byzantine musical notation (U+1D0E8, "Byzantine musical symbol stigma").

In Beta code
Beta code
Beta Code is a method of representing, using only ASCII characters, characters and formatting found in ancient Greek texts . Its aim is to be not merely a romanization of the Greek alphabet, but to represent faithfully a wide variety of source texts – including formatting as well as rare or...

, alphabetic digamma is encoded as "V" (lowercase ϝ) and "*V" (uppercase Ϝ). The numeral sign ("stigma") is encoded as "#2" (lowercase ϛ) and "*#2" (uppercase Ϛ). An additional – now deprecated – code "#4" exists for the ambiguous sign , which can be a glyph variant either of koppa or of stigma. The F-shaped musical notation symbol is "#567", and the subscript stigma notation symbol is "#2232".

In the LaTeX
LaTeX
LaTeX is a document markup language and document preparation system for the TeX typesetting program. Within the typesetting system, its name is styled as . The term LaTeX refers only to the language in which documents are written, not to the editor used to write those documents. In order to...

typesetting system, the "Babel" package allows accessing digamma through the commands "\digamma" (ϝ), "\Digamma" (Ϝ), "\stigma" (ϛ), "\Stigma" (which produces the modern ligature CT glyph ), and "\varstigma" (which produces a variant of the S-shaped form).

Sources

  • Peter T. Daniels – William Bright (edd.), The World's Writing Systems, New York, Oxford University Press, 1996. ISBN 0195079930
  • Jean Humbert, Histoire de la langue grecque, Paris, 1972.
  • Michel Lejeune, Phonétique historique du mycénien et du grec ancien, Klincksieck, Paris, 1967. ISBN 2252034963
  • "In Search of The Trojan War", pp. 142–143,187 by Michael Wood, 1985, published by BBC.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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