1. E. Post, ?Introduction to a general theory of elementary propositions,? Am. J. Math.,43 (1921).
2. S. V. Yablonskii, ?Functional constructions in k-valued logic,? Tr. Steklov Mat. Inst. Akad. Nauk SSSR,51 (1958).
3. I. Rosenberg, ?Über die funktionale Vollständigkeit in den mehrwertigen Logiken,? Rozpravy Ceskoslovenske Akademie Ved.,80, 4 Praha (1970).
4. R.-M. V. Freivald, ?Functional completeness for logic algebra functionsnot defined everywhere,? in Discrete Analysis [in Russian], No. 8, Novosibirsk (1966).
5. B. A. Romov, ?On the formulability of predicates in a finite model,? Kibernetika, Kiev, No. 1 (1971).