Kaigorodov Evgeny Vladimirovich «Hopfian abelian groups» // 2012. №2(18) C.5-12
Fomichev V.M. «ON C-WIDTH OF FINITE NONCYCLIC GROUPS » // 2008. №2(2) C.23-27
Fukson Sofia L. «Orthogonalities in Z
p ⊕ Z
p» // Tomsk State University Journal of Mathematics and Mechanics 2015. №4(36) C.46-54
