@article{GDZPPN001257390, title = {Residual finiteness in permutation varieties of semigroups.}, journal = {Semigroup forum}, volume = {31}, year = {1985}, pages = {33-46}, zbl = {0552.20041}, url = {http://dml.mathdoc.fr/item/GDZPPN001257390} }
Nordahl, T. Residual finiteness in permutation varieties of semigroups.. Semigroup forum, Tome 31 (1985) pp. 33-46. http://gdmltest.u-ga.fr/item/GDZPPN001257390/