Treats phase transition theory and the analysis of phase transitions in terms of both Landau theory and fluctution theory，with particular attention given to crystals and quasicrystals.Also included is an overview of color symmetry applications in phase transition theory.A separate chapter is devoted to maertnsite transitions and this includes an analysis of soliton solutions of nonlinear equsations of elasticity.Revised and expanded translation from the Rusiian edition of 1984.