The article deals with methodological problems during the compiling bilingual indexes. In the basis of the conception of the kind of lexicographic references lies the contemporary notion about lexis as a system. It displays the theoretic formulation of the structure of lexical articles introducing new terminological notions: translation multitude, translation double article (binomial - v matematikata) and triple article (trinominal - v matematikata), translation invariant and variant, translation dominant. After the common theoretic formulations the article represents their concrete appliance in the Slavonic - Greek index to the Old Bulgarian translation of the Book of prophet Ezekiel according to RNB SanktPeterburg F.I.461, performed in collaboration between The Czech Academy of Sciences and The Bulgarian Academy of Sciences.