@Article{PittsAM:parpoe,
  author =	 {A.~M.~Pitts},
  title =	 {Parametric Polymorphism and Operational Equivalence},
  journal =	 {Mathematical Structures in Computer Science},
  year =	 2000,
  volume =	 10,
  pages =	 {321--359},
  issn =	 {0960-1295},
  note =	 {A preliminary version appeared in \emph{Proceedings,
                  Second Workshop on Higher Order Operational
                  Techniques in Semantics (HOOTS II), Stanford CA,
                  December 1997}, Electronic Notes in Theoretical
                  Computer Science 10, 1998.}
}