General approach to control theory based on the methods of Lyapunov

This discussion is an introduction to the second method of Lyapunov in determining the stability of linear and nonlinear control systems. Although almost universally referred to in Russia and although it is becoming an increasingly important concept, this method has not been used in English-speaking countries because of the lack of suitable translations. This introduction to the method will not be published because it is essentially a condensation and introduction of the authors' paper given in Session IV.