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The first represents language expressed as a 2 or 3-character string, the second represents language as a full language tag, the third says "any language" (see Accept-Language and Language Tags in RFC-2616).

In additionAdditionally, each the language defined – optionally in a semicolon-delimited range – may be given an associated quality value ( q=<qvalue> ) which represents an estimate of the user's preference for the languages specified by that range, for example:

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