1. Strongly hereditary radicals;Leavitt, W. G.;Proc. Amer. Math. Soc.,1969
2. Hereditary semisimple classes;Leavitt, W. G.;Glasgow Math. J.,1970
3. On imbeddings of radicals;Rjabuhin, Ju. M.;Bul. Akad. \v{S}tiince RSS Moldoven.,1963
4. Mathematical Expositions, No. 14;Divinsky, Nathan,1965
5. Nonhereditary semisimple classes;Leavitt, W. G.;Proc. Amer. Math. Soc.,1967