I'm editing a chapter that is part of a larger LaTeX project that includes multiple chapters, and I'm trying to use C-c ) to put in a cross reference, but reftex finds only the labels in the current buffer (chapter). According to the reftex manual, pressing x will tell reftex to look in an external document, but that works only if you use the xr package, which I do not need for my document.
Suggestions?
If you use AuCTeX you can use a file local variable to let the chapter file know about the main file and get all labels to be able to refer across all the document. See http://www.gnu.org/software/auctex/manual/auctex/Multifile.html