@article{SF_1990__40_1_135015,
     author = {A. de Luca and S. Varricchio},
     title = {A note on ....-permutable semigroups.},
     journal = {Semigroup forum},
     pages = {153--158},
     publisher = {mathdoc},
     volume = {40},
     number = {1},
     year = {1990},
     zbl = {0687.20052},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__40_1_135015/}
}