Characterization of the automorphisms having the lifting property in the category of Abelian -groups.
Characterization of the inessential endomorphisms in the category of Abelian group.
An endomorphism f of an Abelian group A is said to be inessentia! (in the category of Abelian groups) if it can be extended to an endomorphism of any Abelian group which contains A as a subgroup. In this paper we show that f is as above if and only if (f - v idA)(A) is contained in the rnaximal divisible subgroup of A for some v belonging to Z.
Clones of spaces and maps in homotopy theory.
Cobalanced exact sequences
Complete exact sequences