@article{SF_1978__16_134291,
     author = {B.M. Schein and E.N. Roiz},
     title = {Radicals of semigroups.},
     journal = {Semigroup forum},
     pages = {299--344},
     year = {1978},
     volume = {16},
     zbl = {0393.20047},
     url = {http://geodesic.mathdoc.fr/item/SF_1978__16_134291/}
}