1. Blok, W. J. (1976). Varieties of Interior Algebras, PhD thesis, University of Amsterdam.
2. Blok, W. J. (1980). Pretabular varieties of modal algebras. Studia Logica, 39(2–3), 101–124.
3. Chagrov, A. V. (1989). Nontabularity—pretabularity, antitabularity, coantitabularity. In Algebraic and logical constructions (pp. 105–111). Kalinin: Kalinin State University (Russian).
4. Chagrov, A. V. (1994). Undecidable properties of superintuitionistic logics. In S. V. Jablonskij (Ed.), Mathematical problems of cybernetics (Vol. 5, pp. 67–108). Moscow: Physmatlit (Russian).
5. Chagrov, A., & Zakharyaschev, M. (1997). Modal logic. Oxford: Clarendon Press.