@Article{pearl:01-r282,
  author =    "Pearl, J.",
  title =     "Causal Inference in the Health Sciences: {A}
	       Conceptual Introduction",
  journal =   "Health Services and Outcomes Research Methodology",
  year =      2001,
  volume =    "2",
  note =      "Special issue on {Causal Inference}",
  pages =     "189--220"
}