http://www.rfc-editor.org/rfc/rfc2184.txt
RFC 2184: MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations, N. Freed, K. Moore1997-08-01T23:00:00-00:00This memo defines extensions to the RFC 2045 media type and RFC 2183 disposition parameter value mechanisms. [STANDARDS-TRACK]