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}
}