@article{GDZPPN001261878, title = {Extension properties of WS-groups.}, journal = {Semigroup forum}, volume = {44}, year = {1992}, pages = {63-70}, zbl = {0774.43005}, url = {http://dml.mathdoc.fr/item/GDZPPN001261878} }
Troallic, J.P.; Hansel, G. Extension properties of WS-groups.. Semigroup forum, Tome 44 (1992) pp. 63-70. http://gdmltest.u-ga.fr/item/GDZPPN001261878/