@article{MAN_1964__157_161238,
     author = {A. OBERSCHELP},
     title = {Eigentliche {Klassen} als {Urelemente} in der {Mengenlehre.}},
     journal = {Mathematische Annalen},
     pages = {234--260},
     publisher = {mathdoc},
     volume = {157},
     year = {1964},
     zbl = {0121.25603},
     url = {http://geodesic.mathdoc.fr/item/MAN_1964__157_161238/}
}