1. Some open problems concerning the system E of entailment;Anderson;Acta philosophica Fennica,1963
2. Can the logic of indirect discourse be formalised;Cohen;The journal of symbolic logic,1957
3. Functions of propositions;Cresswell;The journal of symbolic logic,1966
4. The completeness of S0.5;Cresswell;Logique et analyse,1966
5. M. J. Cresswell The completeness of S1 and some related systems Notre Dame journal of formal logic.