1. Åqvist, L. (1967). Good samaritans, contrary-to-duty imperatives, and epistemic obligations. Noûs, 1, 361–379.
2. Dellunde, P., & Godo, L. (2008). Introducing grades in deontic logic. In R. van der Meyden & L. van der Torre (Eds.), DEON 2008 (LNAI, Vol. 5076, pp. 248–262).
3. ∗ Føllesdal, D., & Hilpinen, R. (1970). Deontic logic: An introduction. In R. Hilpinen (Ed.), Deontic logic: Introductory and systematic readings (pp. 1–35). Reidel: Dordrecht. [An old but still very readable introduction to deontic logic.]
4. ∗ Gabbay, D., Horty, J., Parent, X., Meyden, R., & Torre, L. (Eds.) (2013). Handbook of deontic logic and normative systems. (Vol. 1). London: College publications. [Comprehensive coverage of most topics in deontic logic.]
5. Goldman, H. S. (1977). David Lewis’s semantics for deontic logic. Mind, 86, 242–248.