Hair J F et al 1992 Multivariate data analysis 3rd ed New York Macmillan Explains a consistent treatment of objects and their properties see also Introduction to Object Oriented Programming OOP concepts Provides a good entrance to understanding of a consistent treatment of reality in terms of objects like the Linnean classification Basic Concepts of Mathematics by Elias Zakon ISBN 1 931705 00 3 Gives a good entrance to understanding of mathematics May make cladists understand why 1 1 2 and not 1