9. References

   [1] Borenstein N., and N. Freed, "MIME (Multipurpose Internet Mail
       Extensions) Part One:  Mechanisms for Specifying and Describing
       the Format of Internet Message Bodies", RFC 1521, Bellcore,
       Innosoft, September 1993.

   [2] Crocker, D., "Standard for the Format of ARPA Internet Text
       Messages", STD 11, RFC 822, UDEL, August 1982.

   [3] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
       RFC 1340, USC/Information Sciences Institute, July 1992.