1. Das Hyperzentrum einer Gruppe. III;Baer, Reinhold;Math. Z.,1953
2. Nilgruppen;Baer, Reinhold;Math. Z.,1955
3. Nilpotent products of groups;Golovin, O. N.;Mat. Sbornik N.S.,1950
4. Associative operations on groups. I;Moran, S.;Proc. London Math. Soc. (3),1956
5. Associative operations on groups. II;Moran, S.;Proc. London Math. Soc. (3),1958