Analysis of invariant sets

Summary In this paper, an attempt has been made to unify the study of the qualitative and quantitative analysis of systems in a general set up so as to broaden the outlook and applicability of Lyapunov’s second method. Some new notions of quasi-invariant sets are also introduced, which play an important role in application to control theory and differential games. Entrata in Redazione il 29 agosto 1971.