RFC 1521:MIME (Multipurpose Internet Mail Extensio...
RFC-Ref

ANSI


Click on the red underlined text to get to the source

... character set name of "US-ASCII" explicitly refers to ANSI X3.4-1986 [US-ASCII] only. The character set ...


... Coded Character Set--7-Bit American Standard Code for Information Interchange, ANSI X3.4-1986. ...



Google
Web
RFC-Ref