“…This approach is well studied (see, e.g., the articles [6,7,8,9,14,15,16,17,18,19,28,29,30,31] and the monographs [13,20,21,22,23,24]). On the other hand, it is not difficult to see that the principal part { 1 ; } ∈N is not a standard (in other words, classical) system.…”