@article{GDZPPN00124728X,
title = {A proof of the Montague-Plemmons-Schein Theorem on maximal subgroups of the semigroup of binary relations.},
journal = {Semigroup forum},
volume = {1},
year = {1970},
pages = {272-275},
zbl = {0211.03902},
url = {http://dml.mathdoc.fr/item/GDZPPN00124728X}
}
Clifford, A.H. A proof of the Montague-Plemmons-Schein Theorem on maximal subgroups of the semigroup of binary relations.. Semigroup forum, Tome 1 (1970) pp. 272-275. http://gdmltest.u-ga.fr/item/GDZPPN00124728X/