"Semantical Analysis of Modal Logic II: Non-Normal Modal Propositional Calculi", In "The Theory of Models", edited by J. W. Addison, L. Henkin and A. Tarski.
«Semantical Analysis of Modal Logic II: Non-Normal Modal Propositional Calculi», In "The Theory of Models", edited by J. W. Addison, L. Henkin and A. Tarski.