Słowa kluczowe: cardinal characteristic, covering number, uniformity, negations, A Nelson algebras, pseudocomplemented distributive lattices, Kleene algebras., and phrases: modal logic, bisimulation invariance, tableaux, intuitionistic logic, minimal logic, actuality operator, empirical negation, deduction theorem, continuum hypothesis, structure of linear orderings, partition relations., ordered field, 0-definably complete, real closed field