@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/