\documentclass[10pt,a4paper]{article}
\begin{document}

\section{Spell Checking}\label{sec:chk}
Here you can see the spell-checking on different mispelled wrods: Tehy are automaticaly underlined. \textbf{TeX commands} which usually contain text are also checked. Compare \textbf{sec:chk} and \ref{sec:chk} 

\section{Syntax Checking}
Unknown \LaTeX \commands are automatically highlighted.
The same is true for non-matching braces: {  ]

\section{Reference Checking}
Reference are checked for their existence \ref{sec:chk} exists, but \ref{sec:spam} does not. So it's underlined.

\section{Citation Checking}
The same holds for citations: \cite{citation01} and \cite{notInBibliography}. This works both with BiBTeX as with local bibliographies.

\begin{thebibliography}
\bibitem{citation01} This is my paper
\end{thebibliography}



\end{document}
