@article{MAN_1959__138_160712,
     author = {K.H. Hofmann},
     title = {Topologische {Doppelloops} und topologische {Halbgruppen.}},
     journal = {Mathematische Annalen},
     pages = {239--258},
     publisher = {mathdoc},
     volume = {138},
     year = {1959},
     zbl = {0095.02801},
     url = {http://geodesic.mathdoc.fr/item/MAN_1959__138_160712/}
}