H(I) fqM~ ~, for every O~I<~A~M where I <~ A means I is an ideal of A. Note: we write I for the class {1} containing I as its member. A regular class may not contain the ring 0, for the sake of short statement we shall assume that regular classes contain the ring 0. It is well-known that if the class M is regular then ~(M) = {A E H(A) N M = 0}