@article{PORMA_1979__38_1-2_115366,
     author = {Schaefer, Paul},
     title = {Mappings of positive integers and subspaces of m},
     journal = {Portugaliae mathematica},
     pages = {27--38},
     publisher = {mathdoc},
     volume = {38},
     number = {1-2},
     year = {1979},
     mrnumber = {0682353},
     zbl = {0503.47028},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1979__38_1-2_115366/}
}