Exterior Differential Systems - Bryant, Robert L. a Chern, S.S. a Gardner, Robert B. a Goldschmidt, Hubert L. a Griffiths, P.A.

An exterior differential system is a system of equations on a manifold defined by equating to zero a number of exterior differential forms. A system of partial differential equations, with any number of inde­ pendent and dependent variables and involving partial derivatives of any order, can be written as an exterior differential system.