1. BAKER K.A. Finite equational bases for finite algebras in a congruence distributive equational classes. Adv. Math., 1977, v.24, 207–243.
2. BREDIKHIN D.M. Representation of ordered involuted semigroups. Izvestija vuzov, matematika, 1975, No.7, 119–129 (in Russian).
3. CHAGROV A.V. Undecidable properties of extensions of provability logic. I: Algebra i Logika, 1990, v.29, No.3, 350–367; II: ibid., No.5, 613–623. (In Russian)
4. CHAGROV A.V., ZAKHARYASCHEV M.V. The undecidability of the disjunction property of propositional logics and other related problems. J. of Symb. Logic, 1993, v.58, No.3, 967–1002.
5. GOLDBLATT R. Logic of time and computation. CSLI Lecture Notes No.7, 1987.