@article{MZ_1971__123_171630,
     author = {Hans Zassenhaus and Charles E. Johnson},
     title = {On {Equivalence} of {Finite} {Group} {Extensions.}},
     journal = {Mathematische Zeitschrift},
     pages = {191--200},
     publisher = {mathdoc},
     volume = {123},
     year = {1971},
     zbl = {0224.20023},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__123_171630/}
}