@article{MAN_1938__115_159977,
     author = {A. Schmidt},
     title = {\"Uber deduktive {Theorien} mit mehreren {Sorten} von {Grunddingen.}},
     journal = {Mathematische Annalen},
     pages = {485--506},
     publisher = {mathdoc},
     volume = {115},
     year = {1938},
     zbl = {0018.33804},
     url = {http://geodesic.mathdoc.fr/item/MAN_1938__115_159977/}
}