1. Anderson, A. (1958). A reduction of deontic logic to alethic modal logic. Mind, 57, 100–103.
2. Anderson, A. (1968). A new square of opposition: Eubouliatic logic. In Akten des XIV. Internationalen Kongresses für Philosophie (Vol. 2, pp. 271–284). Vienna: Herder
3. Epstein, R. L. (1979). Relatedness and Implication. Philosophical Studies, 36, 137–173.
4. Epstein, R. L. (with the assistance and collaboration of: W. A. Carnielli, I. M. L. D’Ottaviano, S. Krajewski, R. D. Maddux). (1990). The semantic foundations of logic. Volume 1: Propositional logics. Dordrecht: Springer Science+Business Media.
5. Hilpinen, R. Deontic logic. In L. Goble (Ed.) The Blackwell guide to philosopohical logic (pp. 159–182). Oxford: Blackwell Publishers Ltd.