@article{10_21136_CMJ_1970_100962,
     author = {Pond\v{e}l{\'\i}\v{c}ek, Bed\v{r}ich},
     title = {On a certain relation for closure operation on a semigroup},
     journal = {Czechoslovak Mathematical Journal},
     pages = {220--231},
     publisher = {mathdoc},
     volume = {20},
     number = {2},
     year = {1970},
     doi = {10.21136/CMJ.1970.100962},
     mrnumber = {0260905},
     zbl = {0198.34304},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1970.100962/}
}