@article{GDZPPN001249541, title = {Left coset extensions.}, journal = {Semigroup forum}, volume = {7}, year = {1974}, pages = {200-263}, zbl = {0296.20032}, url = {http://dml.mathdoc.fr/item/GDZPPN001249541} }
Grillet, P.A. Left coset extensions.. Semigroup forum, Tome 7 (1974) pp. 200-263. http://gdmltest.u-ga.fr/item/GDZPPN001249541/