1. http://lix.polytechnique.fr/~delaunay/MIME/1521/rfc1521ToC.html
2. http://unix1.sncc.lsu.edu/internet/guides/www-docs/WWW/Protocols/rfc1341/0_TableOfContents.html
3. http://www.oac.uci.edu/indiv/ehood/MIME/MIME.html
4. http://www.ncsa.uiuc.edu/SDG/Software/Mosaic/Docs/mailcap.html
5. http://ccnswww.cityu.edu.hk/email.htm
6. http://jean-luc.ncsa.uiuc.edu/Codes/CoCoBoard/