@article{ARM_1985__21_3_a5,
     author = {Kar\'asek, Ji\v{r}{\'\i}},
     title = {A remark concerning $x$-systems},
     journal = {Archivum mathematicum},
     pages = {177--179},
     publisher = {mathdoc},
     volume = {21},
     number = {3},
     year = {1985},
     mrnumber = {833128},
     zbl = {0594.20061},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1985__21_3_a5/}
}