Various formulation of the Damas-Milner typing discipline for the
functional core of ML.  There is no meta-theory or executable code
in this version.

Author: Robert Harper, transcribed into Elf by Frank Pfenning
Reference: Robert Harper, Systems of Polymorphic Type Assignment in LF,
	   Carnegie Mellon University, Technical Report CMU-CS-90-144,
	   June 1990.
