Teaching a graduate course on AI lead to a paper that "cleaned up" nonlinear planning. Nonlinear planning represents a set of linear (totally ordered) plans as a partially ordered set of actions. The resulting paper with David Rosenblitt appeared in AAAI 1991 and is one of my most cited papers. In 2011 this paper won a 20 year test of time award from the Association for the Advancement of Artificial Intelligence.