\begin{thebibliography}{1}

\bibitem{rfc2543}
M.~Handley, H.~Schulzrinne, E.~Schooler, and J.~Rosenberg,
  \htmladdnormallink{``{SIP:} session initiation
  protocol,''}{http://www.rfc-editor.org/rfc/rfc2543.txt} RFC 2543, Internet
  Engineering Task Force, Mar. 1999.

\end{thebibliography}
