Pfaff's Problem and Its Generalizations

In its simplest form, the Pfaff problem (formulated by Pfaff in 1819) consists of determining the maximal integrable manifold of a Pfaffian system, that is of a system of vector fields in $R^n$. This book offers a solution of this problem and discusses various generalizations, giving an essentially treatment of the theory as it was known in 1949.