# reference undefined at multiple files

I am having touble to getting my labels and references working. I have a multifile-setup where I have the \label in one file and the \ref in the other.

Whatever I do, I always get

./evaluation.tex:420: LaTeX Warning:
Reference EqSoftmax' on page 34 undefined on input line 420.


Does someone know a soliution for this problem?

main.tex

...
\include{systemdescription}
\include{evaluation}
...


systemdescription.tex

...
\begin{align}
\sigma(z_j) = \frac{e^{z_j}}{\sum_{k=1}^{|Z|} e^{z_k}} \;. \label{EqSoftmax}
\end{align}
...


evaluation.tex

...
and applied the softmax function (Equation \ref{EqSoftmax})
...

• Welcome to TeX.Stackexchange! Did you compile more than once? – user36296 Apr 25 '18 at 20:59
• Off-topic for your question, but if you use the cleveref package, it can automatically insert "Equation" if you reference an equation. – user36296 Apr 25 '18 at 21:01
• if you do not have \includeonly` then the cross references will resolve on the second run of latex – David Carlisle Apr 25 '18 at 21:45
• The tag labels is not meant for the referencing system! – user31729 Apr 26 '18 at 7:27
• I'm actually using overleaf.com for my work. So it should have been compiled a lot more often than one time... the \includeonly seems also not to help – cagcoach Apr 26 '18 at 22:35