Some results for implicational calculi
Robert A. Bull · Journal of Symbolic Logic · 1964
I shall refer to the implicational fragment of intuitionist logic, and its extension with the further axiom CCCCpqqrCCCpqrr as IIC and OIC, respectively. The purpose of this paper is to apply a result due to Garrett Birkhoff to the extensions of IIC, and to the extensions of OIC in particular. The main result obtained is that every extension of OIC is characterised by finite models.