1. C.N. Yang, R.L. Mills, Phys. Rev. 96, 191 (1954)
2. Some notions of differential geometry found here are extracted from a) S. Kobayashi, K. Nomizu, “Foundations of Differential Geometry”, Vol. I, II, Interscience, New York 1969 b) W. GREUB, S. HALPERIN, R. VANSTONE, “Connections, Curvature and Cohomology”, Vol. I, II, III, Academic Press, New York 1976
3. S.S. Chern, “Topics in Differential Geometry”, I.A.S. Princeton, 1951
4. C.N. Yang, T.T. Wu, Phys. Rev. D, 12, 3845 (1975), and Stony Brook Preprints ITP SB 76-5, 76-11
5. See, e.g. [2a] Ch. XII and [2b], loc. cit. under the title “Weil Homomorphism”