Antonio Tornambè is a professor and Laura Menini is an associate professor, both in the area "Automatica", which covers both control Theory and robotics. Both of them have been involved in research in those fields generally and, of particular relevance to this book, they have worked on observer design for nonlinear systems (possibly subject to impulsive effects), on stabilization and tracking by state feedback for nonlinear systems, on modeling and control of mechanical systems (possibly subject to impacts), and on control of Hamiltonian systems. They also have wide experience of teaching and their main motivation for writing this book is that of collecting some recent results on the analysis of nonlinear systems, most of them hitherto unpublished, in the mathematical framework that allows both their rigorous derivation and a deep understanding of their meaning and their applicability.