\section*{Contact us}
\addcontentsline{toc}{section}{Conctact us}
\label{sec:contacts}
%\addcontentsline{toc}{section}{Contact us}

If you have any suggestions on how this solution manual may be improved and for any other issue, open an issue on the official repository of the \Wannier{} code on GitHub \url{https://github.com/wannier-developers/wannier90} or send an email on the forum at \newline \texttt{wannier@quantum-espresso.org} (we strongly reccommend the former). 
For the forum note that you will need to be registered. Emails from non-registered users will be deleted automatically. You can register by following the links at
\url{http://www.wannier.org/forum.html}.