“…As a consequence, {p(e a )} a∈A is a basis of B. iii) [12,Theorem 3.15] Moreover, every element of A is equal to σ(•, b) for some unique b ∈ B, and every element of B is equal to σ(a, •) for some unique a ∈ A. iv) The set of all such p with A, B ⊆ Z(G) forms a group under the convolution product. This group is canonically isomorphic to Hom( Z(G), Z(G)), with the isomorphism given by the obvious restriction maps.…”