Woe is me! Marc Greenberg was obliged to jolt my memory to the effect that my Doktorvater, to wit Dean S. Worth, wrote convincingly about the -a' nom/acc plural of masc. nouns in Russian. The reference: Worth, Dean S. "Conditions on a'-plural formation in Russian." Wiener slawistischer Almanach, Bd. 11 (1983): 257-262 Ah well, steady as she goes! John Dingley