FORMAL STRUCTURE OF ELECTROMAGNETICS
General Covariance and Electromagnetics

High-level, explicit treatment of the principle of general covariance as applied to electromagnetics examines the natural invariance of the Maxwell equations, general properties of the medium, nonuniformity, anisotropy and general coordinates in three-space, reciprocity and nonreciprocity, and matter-free space with a gravitational field. 1962 edition.