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2. Anderson, A. R.: 1960, ‘Entailment shorn of modality’ (abstract), J. Symbolic Logic 25, 388.
3. Anderson, A. R.: 1963, ‘Some open problems concerning the system E of entailment’, Acta Philosophica Fennica fasc. 16, 7–18
4. Anderson, A. R. and Belnap, N. D. Jr.: 1959a, ‘Modalities in Ackermann’s “rigorous implication”,’ J. Symbolic Logic 24, 107–111.
5. Anderson, A. R. and Belnap, N. D. Jr.: 1959b, ‘A simple treatment of truth functions’, J. Symbolic Logic 24, 301–302.