The Theory of Classification, Part 5: Axioms, Assertions and Subtyping.

Anthony J. H. Simons The Theory of Classification, Part 5: Axioms, Assertions and Subtyping. 13-22 2003 2 Journal of Object Technology 1 http://www.jot.fm/issues/issue_2003_01/column2.pdf db/journals/jot/jot2.html#Simons03