@inproceedings{siegfried1961unrestricted,
title={Unrestricted nilpotent products},
author={Siegfried Moran},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203159463740941},
booktitle={Acta Mathematica},
volume={108},
number={1},
pages={61-88},
year={1961},
}