\begin{thebibliography}{1}

\bibitem{draft-ietf-sip-callerprefs}
H.~Schulzrinne and J.~Rosenberg, \htmladdnormallink{``Session initiation
  protocol ({SIP}) caller preferences and callee
  capabilities,''}{http://www.ietf.org/internet-drafts/draft-ietf-sip-callerpr%
efs-06.txt} {Internet Draft}, Internet Engineering Task Force, July 2002.
\newblock Work in progress.

\bibitem{draft-ietf-sip-guidelines}
J.~Rosenberg and H.~Schulzrinne, \htmladdnormallink{``Guidelines for authors of
  extensions to the session initiation protocol
  ({SIP}),''}{http://www.ietf.org/internet-drafts/draft-ietf-sip-guidelines-05%
.txt} {Internet Draft}, Internet Engineering Task Force, June 2002.
\newblock Work in progress.

\end{thebibliography}
