Subtyping with Union Types, Intersection Types and Recursive Types.

Flemming M. Damm Subtyping with Union Types, Intersection Types and Recursive Types. 687-706 1994 conf/tacs/1994 TACS db/conf/tacs/tacs94.html#Damm94 http://dx.doi.org/10.1007/3-540-57887-0_121