referencing labels from other files

Question

Sometimes I want to refer (using \ref) a \label from some other tex file. What is the right way to do it?

(It's, of course, possible to \include all files in one and then use \includeonly — but it breaks e.g. page and section numbering.)

Answer 1

http://www.tex.ac.uk/cgi-bin/texfaq2html?label=extref

Answer 2

Use package xr.