@article{MZ_1951__55_169263,
     author = {Wilhelm Ackermann},
     title = {Widerspruchsfreier {Aufbau} einer typenfreien {Logik.}},
     journal = {Mathematische Zeitschrift},
     pages = {364--384},
     publisher = {mathdoc},
     volume = {55},
     year = {1951},
     zbl = {0050.24501},
     url = {http://geodesic.mathdoc.fr/item/MZ_1951__55_169263/}
}