A note on decidability of variables in intuitionistic propositional logic
Katsumasa Ishii · Mathematical logic quarterly · 2018
Abstract An answer to the following question is presented: given a proof in classical propositional logic, for what small set of propositional variables p does it suffice to add all the formulae to Γ in order to intuitionistically prove A? This answer is an improvement of Ishihara's result for some cases.