please refer to the M-M.E.S.S. toolbox by its acronym and the version number. The core copyright holders are Jens Saak, Martin Köhler and Peter Benner. They have to be given as the authors in a citation. The project is frequently updated on Zenodo and every stable release will receive a DOI for proper citation there. The DOI for this version and a sample BibTeX entry can be found below.
The DOI for version 2.2 is 10.5281/zenodo.5938237
@Misc{SaaKB21-mmess-2.2,
author = {Saak, J. and K\"{o}hler, M. and Benner, P.},
title = {{M-M.E.S.S.}-2.1 -- The Matrix Equations Sparse Solvers
library},
month = feb,
year = 2022,
note = {see also:\url{https://www.mpi-magdeburg.mpg.de/projects/mess}},
doi = {10.5281/zenodo.5938237},
key = {MMESS}
}