@article{2194, author = {Specker, Ernst}, title = {Additive Gruppen von Folgen ganzer Zahlen}, journal = {Portugaliae mathematica}, volume = {9}, year = {1950}, pages = {131-140}, zbl = {0041.36314}, mrnumber = {0039719}, language = {en}, url = {http://dml.mathdoc.fr/item/2194} }
Specker, Ernst. Additive Gruppen von Folgen ganzer Zahlen. Portugaliae mathematica, Tome 9 (1950) pp. 131-140. http://gdmltest.u-ga.fr/item/2194/