@article{GDZPPN001247808, title = {On (0,1)-matrix semigroups.}, journal = {Semigroup forum}, volume = {2}, year = {1971}, pages = {74-79}, zbl = {0228.20059}, url = {http://dml.mathdoc.fr/item/GDZPPN001247808} }
Butler, K.K.H. On (0,1)-matrix semigroups.. Semigroup forum, Tome 2 (1971) pp. 74-79. http://gdmltest.u-ga.fr/item/GDZPPN001247808/