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. CONDITION – USED: Books sold are in GOOD or better condition. Good Condition: Minimal damage to the cover, dust jacket may not be included, minimal wear to binding, most of the pages undamaged(e.g., minimal creases or tears), highlighting / underlining acceptable on books as long as the text is readable and markings are not excessive, no missing pages. May be a former library book, with usual treatments(e.g., mylar covers, call stickers, stamps, card pockets, barcodes, or remainder marks). Extra components, such as CDs, DVDs, figurines, or access codes are not included. ISBN: 9780828402217 ISBN10: 0828402213