@article{1256051485, author = {Walker, Carol L.}, title = {Projective classes of cotorsion groups}, journal = {Illinois J. Math.}, volume = {17}, number = {4}, year = {1973}, pages = { 689-706}, language = {en}, url = {http://dml.mathdoc.fr/item/1256051485} }
Walker, Carol L. Projective classes of cotorsion groups. Illinois J. Math., Tome 17 (1973) no. 4, pp. 689-706. http://gdmltest.u-ga.fr/item/1256051485/