@article{JRAM_1970__242_151017,
     author = {Paulo Ribenboim and Tor Gulliksen},
     title = {An elementary note on group-rings.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {148--162},
     publisher = {mathdoc},
     volume = {242},
     year = {1970},
     zbl = {0219.16008},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1970__242_151017/}
}