Preface 1 Overview and introduction 1.1 Historical overview of Bose superfluids 1.2 Summary of chapters 2 Condensate dynamics at T=0 2.1 Gross Pita~vskii (GP) equation 2.2 Bogoliubov equations for condensate fluctuations 3 Coupled equations for the condensate and thermal cloud 3.1 Generalized GP equation for the condensate 3.2 Boltzmann equation for the noncondensate atoms 3.3 Solutions in thermal equilibrium 3.4 Region of validity of the ZNG equations 4 Greens functions and self-energy approximations 4.1 Overview of Greens function approach 4.2 Nonequilibrium Greens functions in normal systems 4.3 Greens functions in a Bose-condensed gas 4.4 Classification of self-energy approximations 4.5 Dielectric formalism 5 The Beliaev and the time-dependent HFB approximations 5.1 Hartree-Fock Bogoliubov self-energies 5.2 Beliaev self-energy approximation 5.3 Beliaev as time-dependent HFB 5.4 Density response in the Beliaev-Popov approximation 6 Kadanoff-Baym derivation of the ZNG equations 6.1 Kadanoff Baym formalism for Bose superfiuids 6.2 Hartree Fock Bogoliubov equations ..............