@article{GDZPPN001261355, title = {Normal semigroups of partial one-to-one transformations II.}, journal = {Semigroup forum}, volume = {43}, year = {1991}, pages = {344-356}, zbl = {0734.20031}, url = {http://dml.mathdoc.fr/item/GDZPPN001261355} }
Williams, W.; Levi, I. Normal semigroups of partial one-to-one transformations II.. Semigroup forum, Tome 43 (1991) pp. 344-356. http://gdmltest.u-ga.fr/item/GDZPPN001261355/