@article{GDZPPN001249576, title = {Semigroups with periodic properties.}, journal = {Semigroup forum}, volume = {7}, year = {1974}, pages = {292-309}, zbl = {0275.22007}, url = {http://dml.mathdoc.fr/item/GDZPPN001249576} }
Day, Jane M. Semigroups with periodic properties.. Semigroup forum, Tome 7 (1974) pp. 292-309. http://gdmltest.u-ga.fr/item/GDZPPN001249576/