Richard T.; Bernard Rosen. Moral Philosophy: A Systematic Introduction to Normative Ethics and Meta-ethics. New York: Macmillan. 1967: 219–220. ISBN 0-02-340580-5
Constitutive Norms in Normative Multiagent Systems. (页面存档备份,存于互联网档案馆) Proceedings of KR 2004. Handbook of Deontic Logic and Normative Systems. [2016-03-18]