@article{MZ_1976__149_172375,
     author = {Ernst Heppner},
     title = {\"Uber die {Dichte} der {Ordnungen} einfacher {Gruppen.}},
     journal = {Mathematische Zeitschrift},
     pages = {17--18},
     year = {1976},
     volume = {149},
     zbl = {0316.20010},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__149_172375/}
}