So sometimes in 1973 there were... '74... there were two concepts of the H2, two nomenclatures of the H2, one was the SD-LD and the other was the class I concept... class I and class II concept that I proposed. It seems like nomenclature squabble, but at issue was something more important, and that was how to... how these two are related to each other. My insistence was that class I and class II are of the same type, that's why the use of a neutral designation of class... class of a something... of a basic similar structure was on the unity of these two, whereas the other concept, the LD-SD emphasised the difference between them so that it appeared that there is something basically different about the class II antigens, the IA antigens. Well, in the end the controversy lasted until the genes were... the products of the genes were isolated and sequenced and to some degree until the genes were cloned, but in the end it turned out to be that I was right.  That the two classes were different in the sense that they were encoded by somewhat differently structured genes but they were both members of the same principle kind. So, the class I and class II nomenclature eventually prevailed and I think the LD-SD is now completely forgotten.