If you use OOFEM, and especially if you use it to accomplish real work, I would like very much to hear from you. A short letter or email describing how you use OOFEM will mean a lot to me. The more people I know are using this program, the more easily I can justify spending time on improvements that I hope will benefit you.
When referencing OOFEM in a publication, please cite at least one of the following papers:
In addition, you can also cite oofem web pages as
OOFEM releases are archived on Zenodo and have DOI, so they are directly citable:
BibTEX file with references is available here.