 An Introduction to Lie Groups and Symplectic Geometry by Robert L. Bryant

Primary text: www.cimat.mx/~gil/docencia/2007/lie/ParkCityLectures.pdf

Lecture 8, Theorem 3, printed p.135: Kähler reduction at zero; central-level qualification, p.136; scalar-circle projective-space example, pp.136–138. The cover identifies the 1991 Park City lectures and the corrected unofficial version of February 19, 2003.