@article{GDZPPN002192020,
title = {Completely semisimple semigroups whose idempotents from a tree.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {281},
year = {1976},
pages = {125-146},
zbl = {0384.20046},
url = {http://dml.mathdoc.fr/item/GDZPPN002192020}
}
Petrich, Mario. Completely semisimple semigroups whose idempotents from a tree.. Journal für die reine und angewandte Mathematik, Tome 281 (1976) pp. 125-146. http://gdmltest.u-ga.fr/item/GDZPPN002192020/