[1] A. Špaček: Statistical Estimation of Provability in Boolean Logics. In: Transactions of the Second Prague Conference on Information Theory, Prague 1959. Prague 1960, 609-626. MR 0123477

[2] A. Špaček: Statistical Estimation of Semantic Provability. In: Proceedings of the Fifth Berkeley Symposium on Mathematical Statistics, 1960, vol. 1, 655-688. MR 0136538

[3] P. R. Halmos: The basic concepts of algebraic logic. American Mathematical Monthly 53 (1956), 363-387. MR 0086028 | Zbl 0070.24506

[4] P. R. Halmos: Algebraic logic II. Homogeneous locally finite polyadic Boolean algebras of infinite degree. Fundamenta Mathematicae 43 (1956), 255 - 325. MR 0086029

[5] P. R. Halmos: Algebraic Logic. Chelsea Publishing Company, New York 1962. MR 0131961 | Zbl 0101.01101

[6] A. Mostowski: Logika matematyczna. PWN, Warszawa-Wroclaw, 1948. MR 0026972