the other user's status. The mechanism behind this is called
\term{Publish-Subscribe} and is specified in XEP-0060~\cite{xep0060}. It can
be used to notify interested users about changes in personal information, and
-implements the well-known Observer pattern.
+implements the well-known Observer pattern~\cite{GOF95}.
A user publishes information by creating a \term{node} on the XMPP server, which
acts as a handle for the data. Interested users can then query the server for
\begin{itemize}
\item an A record \code{capulet.local}, specifying her IP address,
\item an SRV record \code{juliet@capulet.\_presence.\_tcp.local}, specifying
- the port on which her XMPP client listens, and refering to
+ the port on which her XMPP client listens, and referring to
\code{capulet.local} as the host name
\item a PTR record \code{\_presence.\_tcp.local} for service discovery,
pointing to \code{juliet@capulet.\_presence.\_tcp.local}