Katsman A D

Publications in Math-Net.Ru

1. Some types of elements of a semigroup invariant in a group
   
   Uspekhi Mat. Nauk, 11:3(69) (1956),  145–150
2. On some properties of a semigroup invariant in a group
   
   Uspekhi Mat. Nauk, 11:2(68) (1956),  179–183