The following publications are possibly variants of this publication:
- The Theory of Classification, Part 6: The Subtyping InquisitionAnthony J. H. Simons. jot, 2(2):17-26, 2003. [doi]
- The Theory of Classification, Part 4: Object Types and SubtypingAnthony J. H. Simons. jot, 1(5):27-35, 2002. [doi]
- The Theory of Classification, Part 1: Perspectives on Type CompatibilityAnthony J. H. Simons. jot, 1(1):55-61, 2002. [doi]
- The Theory of Classification, Part 7: A Class is a Type FamilyAnthony J. H. Simons. jot, 2(3):13-22, 2003. [doi]