@article{MAN_1970__186_161969,
     author = {H. Walk},
     title = {Bemerkungen \"uber multiplikative {Systeme.}},
     journal = {Mathematische Annalen},
     pages = {36--44},
     year = {1970},
     volume = {186},
     zbl = {0183.47502},
     url = {http://geodesic.mathdoc.fr/item/MAN_1970__186_161969/}
}