1. C. E. Alchourrón. Philosophical foundations of deontic logic and the logic of defeasible conditionals. In Deontic Logic in Computer Science: Normative System Specification, J.-J. Ch. Meyer and R. J. Wieringa, eds. pp. 43–84. John Wiley and Sons, 1993.
2. A. al-Hibri. Deontic Logic: A Comprehensive Appraisal and a New Proposal. University Press of America, Washington, DC, 1978.
3. L. Åqvist and J. Hoepelman. Some theorems about a ‘tree’ system of deontic tense logic. In New Studies in Deontic Logic. R. Hilpinen, ed. pp. 187–221. D. Reidel, Dordrecht, 1981.
4. M. Belzer. Legal reasoning in 3-D. In Proceedings of the First International Conference in Artificial Intelligence and Law. pp. 155–163. ACM Press, Boston, 1987.
5. M. E. Bratman. Intention, Plans and Practical Reason. Harvard University Press, Cambridge, MA, 1987.