1. Rybakov M., Shkatov D. Complexity and expressivity of propositional dynamic logics with finitely many variables // Logic Journal of the IGPL. 2018. V.26. Issue 5. P.539-547.
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2. Rybakov M., Shkatov D. Complexity of finite-variable fragments of propositional modal logics of symmetric frames // Logic Journal of the IGPL. 2019. V.27. Issue 1. P.60-68.
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