@article{JRAM_1976__0283_0284_151721,
     author = {Mario Petrich},
     title = {Completely semisimple semigroups whose idempotents from a tree.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {125--146},
     publisher = {mathdoc},
     volume = {0283_0284},
     year = {1976},
     zbl = {0384.20046},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1976__0283_0284_151721/}
}