Glebskiĭ, Y. V.; Kogan, D. I.; Liogonkiĭ, M. I.; Talanov, V. A. (1969). "Range and degree of realizability of formulas in the restricted predicate calculus". Kibernetika. 5 (2): 17–28. doi:10.1007/bf01071084. S2CID121409759.
Glebskiĭ, Y. V.; Kogan, D. I.; Liogonkiĭ, M. I.; Talanov, V. A. (1969). "Range and degree of realizability of formulas in the restricted predicate calculus". Kibernetika. 5 (2): 17–28. doi:10.1007/bf01071084. S2CID121409759.