1. N. D. Belnap,A Useful Four-Valued Logic, in J. M. Dunn and G. Epstein (eds.) Modern Uses of Multiple-Valued Logics, D. Reidel Publ. Co., Dordrecht.
2. J. M. Dunn,Intuitive Semantics for First-Degree Entailments and ?Coupled Trees? Philosophical Studies 29 (1976), pp. 139?168.
3. J. M. Dunn, andG. Epstein, (eds)Modern Uses of Multiple-Valued Logics D. Reidel Publ. Co., Dordrecht 1977.
4. R. K. Meyer, S. Giambrone andR. T. Brady,Where Gamma Fails Studia Logica 43 (1984), pp. 247?256.
5. R. K. Meyer andJ. K. Slaney,Abelian Logic (from A to Z) in G. Priest, R. Routley and J. Norman (eds)Paraconsistent Logic: Essays on the Inconsistent Philosophia Verlag, M�nchen, 1989.