@article{ARM_1971__7_2_a3,
     author = {Kope\v{c}ek, Old\v{r}ich},
     title = {Das {Produkt} von {H\"ullenstrukturen}},
     journal = {Archivum mathematicum},
     pages = {87--98},
     publisher = {mathdoc},
     volume = {07},
     number = {2},
     year = {1971},
     mrnumber = {0300956},
     zbl = {0259.08006},
     language = {ge},
     url = {http://geodesic.mathdoc.fr/item/ARM_1971__7_2_a3/}
}