A new way of introducing general relativity is presented, with emphasis on the physical meaning of the formalism and on its relation to classical mechanics. The crucial role of the experimental tests is emphasised by pointing out the existence of two inequivalent but equally simple theories, both of which satisfy the principles of general relativity.
Pietenpol, J. L., & Speiser, D. (1975). Remarks on the foundations of general relativity. Helvetica Physica Acta, 48(2), 153-161. https://hdl.handle.net/2078.5/82832 (Original work published 1975)