@article{MAN_1957__133_160562,
     author = {J. Schmidt},
     title = {Die transfiniten {Operationen} der {Ordnungstheorie.}},
     journal = {Mathematische Annalen},
     pages = {439--449},
     year = {1957},
     volume = {133},
     zbl = {0088.26102},
     url = {http://geodesic.mathdoc.fr/item/MAN_1957__133_160562/}
}