@InProceedings{Ring:1993b,
  author = 	"Ring, Mark B.",
  title = 	"Two Methods for Hierarchy Learning in Reinforcement
		 Environments", 
  booktitle = 	"From Animals to Animats 2: Proceedings of the Second
		 International Conference on Simulation of Adaptive Behavior",
  year = 	1993,
  editor = 	"Meyer, J. A. and Roitblat, H. and Wilson, S.",
  pages = 	"148--155",
  publisher = 	"MIT Press",
}