@techreport{Forbus,
  author	= {Forbus, K. and Stevens, A.},
  month		= mar,
  year		= {1981},
  title		= {Using Qualitative Simulation to Generate Explanations},
  number	= {4490},
  note		= {Also appeared in @i(Cognitive Science) 3, 1981.},
  institution	= {Bolt Beranek and Newman, Inc.}
}