Of interest to everybody working on perturbation theory in differential equations, this book requires only a standard mathematical background in engineering and

Perturbation methods have always been an important tool for treating nonlinear differential equations. Now the drudgery associated with them has been eliminated

Perturbation theory and in particular normal form theory has shown strong growth in recent decades. This book is a drastic revision of the first edition of the

This book is developed for the study of vectorial problems in the calculus of variations. The subject is a very active one and almost half of the book consists