Dechter, Rina, Sutton, Richard S. and Kearns, Michael J., eds. 2002. AAAI-02. Proceedings of the Eighteenth National Conference on Artificial Intelligence. Menlo Park, California: The AAAI Press.
Sutton, Richard S., Precup, Doina and Singh, Satinder P. 1999. “Between MDPs and semi-MDPs: A Framework for Temporal Abstraction in Reinforcement Learning.”Artificial Intelligence 112(1–2): 181–211.