“…The operators on this set of functions are (infinite) matrices F m,m , where m and m are double indices, m = (m 1 , m 2 ), m = (m 1 , m 2 ), and m 1 , m 2 , m 1 , m 2 ∈ Z. In order to develop our construction, we embed a subspace of these matrices in the set of some special objects; by analogy with the continuous case, these objects will be called extended operators; see [3]- [6].…”