\begin{thebibliography}{1}

\bibitem{rfc2119}
S.~Bradner, ``Key words for use in {RFCs} to indicate requirement levels,'' RFC
  2119, Internet Engineering Task Force, Mar. 1997.

\bibitem{draft-lennox-sip-cgi}
J.~Lennox, J.~Rosenberg, and H.~Schulzrinne, ``Common gateway interface for
  {SIP},'' {Internet Draft}, Internet Engineering Task Force, Nov. 1998.
\newblock Work in progress.

\bibitem{draft-ietf-iptel-cpl-requirements}
H.~Schulzrinne and J.~Lennox, ``Call processing language requirements,''
  {Internet Draft}, Internet Engineering Task Force, Aug. 1998.
\newblock Work in progress.

\bibitem{draft-ietf-mmusic-sip-cc}
H.~Schulzrinne and J.~Rosenberg, ``{SIP} call control services,'' {Internet
  Draft}, Internet Engineering Task Force, Feb. 1998.
\newblock Work in progress.

\bibitem{draft-ietf-conneg-feature-syntax}
G.~Klyne, ``A syntax for describing media feature sets,'' {Internet Draft},
  Internet Engineering Task Force, Dec. 1998.
\newblock Work in progress.

\end{thebibliography}
