@article{10_21136_CMJ_1971_101006,
     author = {Pond\v{e}l{\'\i}\v{c}ek, Bed\v{r}ich},
     title = {A certain equivalence on a semigroup},
     journal = {Czechoslovak Mathematical Journal},
     pages = {109--117},
     publisher = {mathdoc},
     volume = {21},
     number = {1},
     year = {1971},
     doi = {10.21136/CMJ.1971.101006},
     mrnumber = {0283110},
     zbl = {0217.36404},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1971.101006/}
}