@article{SF_1974__7_134009,
     author = {P.A. Grillet},
     title = {Left coset extensions.},
     journal = {Semigroup forum},
     pages = {200--263},
     publisher = {mathdoc},
     volume = {7},
     year = {1974},
     zbl = {0296.20032},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__7_134009/}
}