@article{10_21136_CMJ_1974_101234,
     author = {Kope\v{c}ek, Old\v{r}ich and Novotn\'y, Miroslav},
     title = {On some invariants of unary algebras},
     journal = {Czechoslovak Mathematical Journal},
     pages = {219--246},
     year = {1974},
     volume = {24},
     number = {2},
     doi = {10.21136/CMJ.1974.101234},
     mrnumber = {0347703},
     zbl = {0333.08004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1974.101234/}
}