@TechReport{pearl:13-r420,
  author = 	 "Pearl, J.",
  title = 	 "Reflections ons {Heckman} and {Pinto's} 
		 `Causal Analysis After {Haavelmo}'",
  institution =  "Department of Computer Science, University of California, 
                  Los Angeles",
  address = 	 "CA",
  year = 	 2013,
  number =	 "R-420, {$<$http://ftp.cs.ucla.edu/pub/stat\_ser/r420.pdf$>$}",
  note = 	 "Working paper"
}