@article{MZ_1953__58_169355,
     author = {Alfred L. Foster},
     title = {Generalized },
     journal = {Mathematische Zeitschrift},
     pages = {306--336},
     publisher = {mathdoc},
     volume = {58},
     year = {1953},
     zbl = {0051.02201},
     url = {http://geodesic.mathdoc.fr/item/MZ_1953__58_169355/}
}