# Cross-referencing between different files with LaTeX

Sometimes I want to refer labels I placed in external .tex files. I mean, I want o refer (using the command \ref) a \label from a .tex file I created in another project.

A valid solution it to use the command \include. But I in this case I don’t want to include the .tex, I only want to be able to refer their labels.

This can be done using the xr package. The command \externaldocument allows to include an external .tex file (without adding its content to the current file) and use \ref like normal.

For example, being in my_doc.tex I want o refer a label in ../thesis/thesis.tex. We add into the preamble:

\usepackage{xr}
\externaldocument{../thesis/thesis}


And then, in the document we can do \ref{chp1:f:miRNA-mechanism}.

WARNING: The package looks for the aux file, so it does not work in all settings and, more importantly, without a full document. So, if I want to refer the labels in chapter1.tex, that is added to thesis.tex with an \include, I still need to run the \externaldocument{../thesis/thesis} instead of \externaldocument{../thesis/chapter1}.