A criterion for admissibility of rules in the model system S4 and the intuitionistic logic

G. E. Mints, "Admissible and arbitrary rules," Zap. Nauchn. Sem. LOMI Akad. Nauk SSSR,8, 189–191 (1968).

G. E. Mints, "Arbitrariness of admissible rules," J. Sov. Math.,6, No. 4 (1976).

V. V. Rybakov, "Admissible rules of pretable modal logics," Algebra Logika,20, No. 4, 440–464 (1981).

V. V. Rybakov, "The decidability of the admissibility problem in extensions of the logic S4.3," Sixth All-Union Conf. of Math. Logic, Lecture Theses, Tbilisi (1982), p. 158.

V. V. Rybakov, "The decidability of the admissibility problem in finite-layer modal logics," Algebra Logika,23, No. 1, 100–116 (1984).

V. V. Rybakov, "Elementary theories of free closure algebras," Sixteenth All-Union Conf. on Algebra, Lecture Theses, Leningrad (1981), p. 116.

A. I. Tsitkin, "On admissible rules in the intuitionistic propositional logic," Mat. Sb.,102, No. 2, 314–323 (1977).

A. I. Tsitkin, "On structurally complete superintuitionistic logics," Dokl. Akad. Nauk SSSR,241, No. 1, 40–43 (1978).

H. Freedman, "A hundred and two problems in mathematical logic," J. Symb. Logic,40, No. 2, 113–130 (1975).

R. Harrop, "Concerning formulas of the types A→BVC, A→∃×B(x) in intuitionistic formal systems," J. Symb. Logic,25, No. 1, 27–32 (1960).

J. Port, "The deducibilities of S5," J. Philos. Logic,10, 409–422 (1981).

K. Segerberg, "An essay in classical modal logic," University of Uppsala, Uppsala (1971).