\documentstyle[refcheck,11pt]{article}
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\begin{document}
\baselineskip=4.5mm
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\parindent=1em
\parskip=0.75ex

\def\RefCheck{Ref\kern0.15em Check}

\showrefnames
\showcitenames

\section*{\RefCheck\ for \LaTeX~2.09}
\markboth{\protect\bf\RefCheck\ for \LaTeX~2.09}%
{\protect\bf\RefCheck\ for \LaTeX~2.09}
This demo file is to describe usage of {\tt \RefCheck} package
with \LaTeX~2.09. The package looks for useless labels,
unlabelled equations and unused bibliography references.

To start checking one should just write
\begin{verbatim}
     \documentstyle[refcheck]{article}
\end{verbatim}
at the beginning of document and compile the file twice.
Then, comments on references could be found in LOG file.

Consider the set of equations
\begin{eqnarray}
&&a=b\label{eq.1}\\
&&b=c\label{eq.2}\\
&&c=d,
\end{eqnarray}
written as
\begin{verbatim}
     \begin{eqnarray}
     &&a=b\label{eq.1}\\
     &&b=c\label{eq.2}\\
     &&c=d,
     \end{eqnarray}
\end{verbatim}
Then the LOG file will contains the following messages:
{\small
\begin{verbatim}
 LaTeX Warning: Unused label `eq.2' on page 1 on input line 33.
 LaTeX Warning: Unlabelled equation (3) on page 1 on input line 35.
\end{verbatim}
}
\noindent
because the equation (\ref{eq.1}) is
referenced here by \verb#(\ref{eq.1})#, the label {\tt eq.2} of the second
equation isn't used and the last equation is numbered and
unlabelled.

The labels identifiers on the marginal notes are stated by
the command
\begin{verbatim}
     \showrefnames
\end{verbatim}
These marks include some information on labels.
Namely, the useless labels are underlined and bounded by `{\tt 
?}', the mark `{\tt ???}' means that the equation is unlabelled.  
The marks are framed for labels which are used in text.  This 
regime can be set off in any point of text by the command 
\begin{verbatim}
     \norefnames
\end{verbatim}
\newpage

The package is working in the same way with bibliography.
Consider the short list of books:

\vspace{-1\baselineskip}

\begin{thebibliography}{9}
\bibitem{book1}A book.
\bibitem{book2}Another book.
\bibitem{book3}Third book.
\end{thebibliography}
defined as follows
\begin{verbatim}
     \begin{thebibliography}{9}
     \bibitem{book1}A book.
     \bibitem{book2}Another book.
     \bibitem{book3}Third book.
     \end{thebibliography}
\end{verbatim}
Further, we use the labels of \cite{book1,book2} with the
command \verb#\cite{book1,book2}# and do not use the label
`book3'. Then, the LOG file will contain the following message
{\small
\begin{verbatim}
 LaTeX Warning: Unused bibitem `book3' on page 2 on input line 79.
\end{verbatim}}

Commands \verb#\showcitenames# and \verb#\nocitenames#
for bibliography are analogous to the commands
\verb#\showrefnames# and \verb#\norefnames#. They set on and off
\TeX\ to write to output labels of bibitems.

\vspace{2\baselineskip}

\underline{{\sc Note}} the problem with implicitly cited labels.
For example, if there is a set of equations which are labelled
with $\,${\tt a1,a2,...an}$\,$ and referred in document by
\verb#(\ref{a1})--(\ref{an})#, then the labels $\,${\tt
a2,a3,...an-1}$\,$ cannot be recognized to be `used'.


\end{document}