@article{GDZPPN001249681,
title = {Semigroups for which every S-system has the natural partial order.},
journal = {Semigroup forum},
volume = {7},
year = {1974},
pages = {51-55},
zbl = {0284.20064},
url = {http://dml.mathdoc.fr/item/GDZPPN001249681}
}
McMorris, F.R.; Johnson, C.S. jr. Semigroups for which every S-system has the natural partial order.. Semigroup forum, Tome 7 (1974) pp. 51-55. http://gdmltest.u-ga.fr/item/GDZPPN001249681/