@article{GDZPPN001262785, title = {Permutable transformation semigroups.}, journal = {Semigroup forum}, volume = {46}, year = {1993}, pages = {123-125}, zbl = {0792.20060}, url = {http://dml.mathdoc.fr/item/GDZPPN001262785} }
Ehrenfeucht, A.; Rozenberg, G.; Harju, T. Permutable transformation semigroups.. Semigroup forum, Tome 46 (1993) pp. 123-125. http://gdmltest.u-ga.fr/item/GDZPPN001262785/