Два замечания о строго импликативных формулах в модальной логике s3.

Abstract

Some questions about strict implication in modal system S3 are discussed. The first theorem shows that strict implication formulas have the property of equivalent replacement; as well known the logic S3 has not the full theorem of equivalent replacement. The second theorem of the paper is connected with an open question [4] on description of one variable strict implication fragment of S3: this fragment contains at least 29 non-equivalent formulas; in the author's paper [2] the number was 24.