diff --git a/books/bookvol2.pamphlet b/books/bookvol2.pamphlet
index 869c1e7..da71de9 100644
--- a/books/bookvol2.pamphlet
+++ b/books/bookvol2.pamphlet
@@ -299,6 +299,85 @@ November 10, 2003 ((iHy))
 \eject
 \pagenumbering{arabic}
 \setcounter{chapter}{0} % Chapter 1
+\chapter{Axiom and Category Theory}
+\section{Covariance and Contravariance}
+Axiom has an order relation between types. The types can be in one of
+five possible relationships. 
+
+A type can be more general than another type. For example, Integer is
+more general than PositiveInteger.
+
+A type can be more specific than another type. Conversely PositiveInteger
+is more specific than Integer.
+
+A type can be equal to another type. 
+
+A type can be converted or coerced to another type. For example, 
+Fraction(Polynomial(Integer)) can be coerced to Polynomial(Fraction(Integer)).
+
+A type can be unrelated to another type. String and Expression are not related.
+
+Covariance is converting from a wider type to a narrower type. 
+For instance, converting from Matrix(Float) to Matrix(Integer).
+
+Contravariance is converting from a narrower type to a wider type.
+For instance, converting from Matrix(Integer) to Matrix(Float).
+
+Invariance means that one type cannot convert to another.
+For instance, a Matrix(Float) which contains numbers which cannot
+be represented as Integers cannot be converted to a Matrix(Integer).
+
+These facts form an order relation, which by definition is reflexive,
+transitive and antisymmetric. 
+
+Reflexive means that Integer = Integer.
+
+Transitive means that PositiveInteger $<$ Integer $<$ Float implies
+that PositiveInteger $<$ Float.
+
+Antisymmetric means that PositiveInteger $<$ Float implies
+not(Float $<$ PositiveInteger).
+
+\section{Axiom Type Lattice}
+
+The types in Axiom form a lattice based on the order relationship.
+It is a lattice because Axiom supports multiple inheritance.
+
+References of interest include:
+
+Michael Barr and Charles Wells
+``Category Theory for Computing Science'' 1998\\
+\verb|www.math.mcgill.ca/triples/Barr-Wells-ctcs.pdf|
+
+Saunders Mac Lane
+``Catogories for the Working Mathematician''\\
+Springer-Verlag 2010 ISBN 978-1-4419-3123-8 
+
+Steve Awodey
+``Category Theory''\\
+\verb|ftp://sumin.in.ua/Books/DVD-021/Awodey_S._Category_Theory(en)(305s).pdf|
+
+``Introduction to Category Theory''\\
+\verb|www.youtube.com/watch?v=eu0rj5C2Otg|
+
+Luca Cardelli and Peter Wegner
+``On understanding types, data abstraction and polymorphism''
+Computing Surveys, Vol 17 no 4 pp471-522 Dec. 1985\\
+\verb|lucacardelli.name/Papers/OnUnderstanding.A4.pdf|
+
+A. J. H. Simons,
+``Adding Axioms to Cardelli-Wegner Subtyping'' 1994\\
+\verb|staffwww.dcs.shef.ac.uk/people/A.Simons/research/reports/addaxiom.pdf|
+
+Dana Scott
+``Data Types as Lattices''\\
+\verb|www.cs.ox.ac.uk/files/3287/PRG05.pdf|
+
+Roland Backhouse and Marcel Bijsterveld
+``Category Theory as Coherently Constructive Lattice Theory''
+November 1994
+
+\chapter{Implementation Details}
 \section{Makefile}
 This book is actually a literate program\cite{2} and can contain 
 executable source code. In particular, the Makefile for this book
diff --git a/changelog b/changelog
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+20130314 tpd src/axiom-website/patches.html 20130314.11.tpd.patch
+20130314 tpd books/bookvol2 Axiom and Category Theory chapter
 20130314 tpd src/axiom-website/patches.html 20130314.10.tpd.patch
 20130314 tpd buglist  MLIFT fix 20001, add 20568
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 <a href="patches/20130314.10.tpd.patch">20130314.10.tpd.patch</a>
 books/bookvol10.3 MLIFT fix 20001, add 20568
+<a href="patches/20130314.11.tpd.patch">20130314.11.tpd.patch</a>
+books/bookvol2 Axiom and Category Theory chapter
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