@misc{Maechler2021,
author = {Maechler, M. and Rousseeuw, P. and Struyf, A. and Hubert, M. and Studer, M. and Hornik, K.},
title= {cluster: Cluster analysis basics and extensions. R package version 2.1.2},
year = {2021},
URL = {https://cran.r-project.org/package=cluster},
}