Inference rules with metavariables, and logical equations in the pretabular modal logic PM1
V. R. Kiyatkin

This publication is cited in the following articles:

1. A. N. Rutskii, “An admissibility criterion for inference rules with metavariables in the modal logic $S4.\alpha_N$”, Siberian Math. J., 48:2 (2007), 317–326          
2. E. M. Golovanova, “A criterion for admissibility of inference rules in some class of $S4$-logics without the branching property”, Siberian Math. J., 44:4 (2003), 568–576