@article{ARM_1979_15_4_a3,
     author = {J\"urgensen, H.},
     title = {Disjunktive {Teilmengen} inverser {Halbgruppen}},
     journal = {Archivum mathematicum},
     pages = {205--207},
     year = {1979},
     volume = {15},
     number = {4},
     mrnumber = {563148},
     zbl = {0439.20044},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/ARM_1979_15_4_a3/}
}