“…Subsequently, various works were produced which studied and generalized the unitary divisibility relation and associated convolution (see [8,16,19,31]). In several cases, entire classes of A-functions were introduced, viewing the usual divisibility relation (which corresponds to the A-function D) and the unitary divisibility relation as the first two elements of a sequence of A-functions that preserved some property or theme (see [1,3,9,10,17,28]).…”