How to refer to labels in other documents?

How to refer to labels in other documents? 

\usepackage{xr}
\externaldocument{supplement}
...
\ref{ext:supplement}

http://tex.stackexchange.com/questions/160140/how-to-refer-to-labels-in-other-documents

How to remove the link

http://tex.stackexchange.com/questions/118182/selectively-turn-off-hyperref-links-for-citations