@article{CM_1937__4__235_0,
     author = {Freudenthal, Hans},
     title = {Bettische {Gruppe} mod. 1 und {Hopfsche} {Gruppe}},
     journal = {Compositio Mathematica},
     pages = {235--238},
     publisher = {Johnson Reprint Corporation},
     volume = {4},
     year = {1937},
     zbl = {0016.28102},
     language = {de},
     url = {http://www.numdam.org/item/CM_1937__4__235_0/}
}