@article{GDZPPN001248073, title = {Projectivity of acts and Morita equivalence of monoids.}, journal = {Semigroup forum}, volume = {2}, year = {1971}, pages = {359-370}, zbl = {0231.18013}, url = {http://dml.mathdoc.fr/item/GDZPPN001248073} }
Knauer, U. Projectivity of acts and Morita equivalence of monoids.. Semigroup forum, Tome 2 (1971) pp. 359-370. http://gdmltest.u-ga.fr/item/GDZPPN001248073/