Nonperturbative quantum field theory means the evaluation and investigation of quantum field theory be yond perturbation theory, andincludes a wide range o fp rob lems. It has been one oft he most fascinating topics of theoretical physical research in the past few decades and, in addition, it is closely linked with the investigation ofthe structure ofmatter. That isw hy an enormous number of papers has been de voted tot he treatment oft hese problems, and it would go beyond the scope of this preface - and even oft he whole book - to give areview of these developments. Thus we confine...