To cite MueLu, please use the following bibliography entries.

@techreport{MueLu,
title={Mue{L}u User’s Guide},
author={Luc Berger-Vergiat and Christian A. Glusa and Jonathan J. Hu and Matthias Mayr and Andrey Prokopenko and Christopher M. Siefert and Raymond S. Tuminaro and Tobias A. Wiesner}, number={SAND2019-0537}, year={2019}, institution = {Sandia National Laboratories}, }

@Misc{MueLuURL,
author={Luc Berger-Vergiat and Christian A. Glusa and Jonathan J. Hu and Matthias Mayr and Andrey Prokopenko and Christopher M. Siefert and Raymond S. Tuminaro and Tobias A. Wiesner}, title = {{M}ue{L}u multigrid framework}, howpublished = {\url{http://trilinos.org/packages/muelu\}\}, year = {2019} }