@article{SF_1984__28_134648,
     author = {A. Varisco and A. Cherubini},
     title = {Permutable duo semigroups.},
     journal = {Semigroup forum},
     pages = {155--172},
     publisher = {mathdoc},
     volume = {28},
     year = {1984},
     zbl = {0524.20040},
     url = {http://geodesic.mathdoc.fr/item/SF_1984__28_134648/}
}