@article{2876, author = {Schaefer, Paul}, title = {Mappings of positive integers and subspaces of m}, journal = {Portugaliae mathematica}, volume = {38}, year = {1979}, pages = {27-38}, zbl = {0503.47028}, mrnumber = {0682353}, language = {en}, url = {http://dml.mathdoc.fr/item/2876} }
Schaefer, Paul. Mappings of positive integers and subspaces of m. Portugaliae mathematica, Tome 38 (1979) pp. 27-38. http://gdmltest.u-ga.fr/item/2876/