ABNF
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This specification makes use of the Augmented Backus-Naur Form (ABNF)
[RFC4234] notation, including the core rules ...
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Note that this syntax is somewhat more restrictive than what is
allowed by the ABNF in [RFC2045].
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Note that this syntax is somewhat more restrictive than what is
allowed by the ABNF in [RFC2045] and amended by [RFC2231].
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... Crocker, D. Ed., and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 4234draft, October 2005. ...