ABSTRACT
Let G be a finite abelian group and let A and B be subsets of G. The sum A+B of the subsets A and B is defined to be the set of elements
a+ b, a ∈ A, b ∈ B.
If the elements on the list a + b, a ∈ A, b ∈ B are distinct, then we say that the sum A+B is direct.
