@article{SF_1970__1_133782,
     author = {A.H. Clifford},
     title = {Radicals in semigroups.},
     journal = {Semigroup forum},
     pages = {103--127},
     year = {1970},
     volume = {1},
     zbl = {0209.04801},
     url = {http://geodesic.mathdoc.fr/item/SF_1970__1_133782/}
}