@article{SF_1980__19_134392,
     author = {Y. Kobayashi},
     title = {The exponent semigroup of a semigroup satisfying {(XY)3} = x3 {Y3.}},
     journal = {Semigroup forum},
     pages = {323--330},
     year = {1980},
     volume = {19},
     zbl = {0433.20041},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__19_134392/}
}