Back, A., Carmo, M. P. D., & Hsiang, W. Y. (2009). On Some Fundamental Equations of Equivariant Riemannian Geometry. Tamkang Journal of Mathematics, 40(4), 343-376. https://www.airitilibrary.com/Article/Detail?DocID=00492930-200912-201012230067-201012230067-343-376