@inproceedings{Sacerdoti73,
  author	= {Sacerdoti, Earl},
  month		= aug,
  year		= {1973},
  title		= {Planning in a Hierarchy of Abstraction Spaces},
  booktitle	= {Proceedings of IJCAI III},
  pages		= {412--422},
  organization	= {International Joint Conference on Artificial Intelligence}
}