Dear Tsuji, Ukrainian Vocative for Valera (feminine paradigm) would be Valero, not Valeru; -u ending is used for grammatical neuters such as dido-didu, tato-tatu and for some masculines such as Jarko-Jarku, Levko-Levku, and Ihor-Ihorju. My question is, where did this happen? In Russia? And how old was the person? Alla Nedashkivska