MIME RFCs
1521 "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies"
1522 "MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text"
1524 “A User Agent Configuration Mechanism for Multimedia Mail Format Information”, 09/23/1993
1563 "The text/enriched MIME Content-type"