@article{SF_1981__23_134515,
     author = {Aldo de Luca and Antonio Restivo},
     title = {A synchronization property of pure subsemigroups.},
     journal = {Semigroup forum},
     pages = {233--240},
     year = {1981},
     volume = {23},
     zbl = {0487.68075},
     url = {http://geodesic.mathdoc.fr/item/SF_1981__23_134515/}
}