@article{ELMA_1963__18_140765,
     author = {Peter Scherk},
     title = {\"Uber {Summen} von {Mengen} nat\"urlicher {Zahlen.}},
     journal = {Elemente der Mathematik},
     pages = {49--54},
     publisher = {mathdoc},
     volume = {18},
     year = {1963},
     zbl = {0112.27403},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1963__18_140765/}
}