@article{MZ_1961__77_169974,
     author = {Manfred Breuer},
     title = {Zum {Pfaffschen} {Problem.}},
     journal = {Mathematische Zeitschrift},
     pages = {63--67},
     publisher = {mathdoc},
     volume = {77},
     year = {1961},
     zbl = {0107.30002},
     url = {http://geodesic.mathdoc.fr/item/MZ_1961__77_169974/}
}