Introduction.- Basic Properties of Quasivarieties.- Commutator Equations and the Equationally Defined Commutator.- Centralization Relations.- Additivity of the Equationally Defined Commutator.- Modularity and Related Topics.- Additivity of the Equationally Defined Commutator and Relatively Congruence-Distributive Dub quasivarieties.- More on Finitely Generated Quasivarieties.- Commutator Laws in Finitely Generated Quasivarieties.- Appendix 1: Algebraic...