@PhdThesis{Elliot90:Dissertation,
  author       = {Conal Elliott},
  title        = {Extensions and Applications of Higher-Order Unification},
  url          = {http://conal.net/papers/elliott90.pdf},
  school       = {School of Computer Science, Carnegie Mellon University},
  year         = 1990,
  note         = {Available as Technical Report {CMU-CS-90-134}}
}