Kim B. Bruce Joseph Vanderwaart Semantics-Driven Language Design: Statically Type-safe Virtual Types in Object-oriented Languages. 1999 20 Electr. Notes Theor. Comput. Sci. http://www.elsevier.com/gej-ng/31/29/23/44/23/show/Products/notes/index.htt#004 db/journals/entcs/entcs20.html#BruceV99