@article{SF_1994__48_3_135298,
     author = {A. Nagy},
     title = {Permutation functions and (n,m)-commutativity of semigroups .},
     journal = {Semigroup forum},
     pages = {71--78},
     publisher = {mathdoc},
     volume = {48},
     number = {3},
     year = {1994},
     zbl = {0805.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1994__48_3_135298/}
}