\chapcontents {1}{Preface}{3}
\chapcontents {2}{2d-objects}{4}
\seccontents {2.1}{Introduction} {4}
\seccontents {2.2}{Crossed modules} {5}
\seccontents {2.3}{Pre-crossed modules} {7}
\seccontents {2.4}{Cat1-groups and pre-cat1-groups} {8}
\seccontents {2.5}{Selection of a small cat1-group} {10}
\chapcontents {3}{2d-mappings}{11}
\seccontents {3.1}{Morphisms of pre-crossed modules} {11}
\seccontents {3.2}{Morphisms of pre-cat1-groups} {12}
\seccontents {3.3}{Operations on morphisms} {13}
\chapcontents {4}{Derivations and Sections}{15}
\seccontents {4.1}{Whitehead Multiplication} {15}
\seccontents {4.2}{Whitehead Groups and Monoids} {17}
\chapcontents {5}{Actors of 2d-objects}{19}
\seccontents {5.1}{Actor of a Crossed Module} {19}
\chapcontents {6}{Induced Constructions}{21}
\seccontents {6.1}{Induced crossed modules} {21}
\chapcontents {7}{Utility functions}{24}
\seccontents {7.1}{Inclusion and Restriction Mappings} {24}
\seccontents {7.2}{Endomorphism Classes and Automorphisms} {24}
\seccontents {7.3}{Abelian Modules} {26}
\seccontents {7.4}{Distinct and Common Representatives} {26}
\chapcontents {8}{Development History}{27}
\seccontents {8.1}{Versions 2.002 -- 2.005} {28}
\seccontents {8.2}{Version 2.006} {28}
\seccontents {8.3}{What needs doing next?} {29}
\chapcontents {}{Bibliography}{30}
\chapcontents {}{Index}{31}
