@article{MASLO_1994__44_1_a5,
     author = {Abrhan, Imrich and Satko, Ladislav},
     title = {$r$-systems of unary algebras. {I:} {On} maximal and greatest $J$-classes of the direct product of unary algebras},
     journal = {Mathematica slovaca},
     pages = {55--68},
     publisher = {mathdoc},
     volume = {44},
     number = {1},
     year = {1994},
     mrnumber = {1290273},
     zbl = {0799.08006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1994__44_1_a5/}
}