\begin{sf}
\begin{tabular}{lclcl}
Contact & = & ( "Contact" $|$ "m" ) ":" \\
        &   & ("*" $|$ (1\# (( name-addr $|$ addr-spec )\\
        &   & *( ";" contact-params ))))\\
name-addr    & = & [ display-name ] "$<$" addr-spec "$>$"\\
addr-spec    & = & SIP-URL $|$ URI \\
display-name & = & *token $|$ quoted-string\\  
\end{tabular}
\end{sf}

\begin{sf}
\begin{tabular}{lclcl}
contact-params 
&$=$& "q"            & "=" & qvalue\\
&$|$& "action"       & "=" & "proxy" $|$ "redirect"\\
&$|$& "expires"      & "=" & delta-seconds $|$ $<$"$>$ SIP-date $<$"$>$\\
&$|$& \multicolumn{2}{l}{contact-extension}\\
contact-extension
&$=$& generic-param\\
qvalue               & = & ( "0" [ "." 0*3DIGIT ] )\\
                     &$|$& ( "1" [ "." 0*3("0") ] )
\end{tabular}
\end{sf}
