@article{ARM_1965_1_1_a2,
     author = {Havel, V\'aclav},
     title = {Unessential {Zassenhaus} refinements},
     journal = {Archivum mathematicum},
     pages = {35--38},
     year = {1965},
     volume = {1},
     number = {1},
     mrnumber = {0194367},
     zbl = {0188.04204},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1965_1_1_a2/}
}