@article{SF_1996__53_2_135481,
     author = {M. Gutan},
     title = {A problem on semigroups satisfying permutation identities.},
     journal = {Semigroup forum},
     pages = {173--183},
     publisher = {mathdoc},
     volume = {53},
     number = {2},
     year = {1996},
     zbl = {0861.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1996__53_2_135481/}
}