J. J. Duistermaat, G. J. Heckman. On the Variation in the Cohomology of the Symplectic Form of the Reduced Phase Space. Inventiones mathematicae. 1982.
J. J. Duistermaat, G. J. Heckman. On the Variation in the Cohomology of the Symplectic Form of the Reduced Phase Space. Inventiones mathematicae. 1982.