EDDINGTON, Relativitätstheorie in mathematischer Behandlung, 1925

First German edition of The Mathematical Theory of Relativity published in 1923.
This German edition contains as an appendix an original article by Einstein on Eddington's theory and Hamilton's principle.
Arthur Eddington, a leading physicist, was the first to provide experimental proof of Einstein's general relativity during the solar eclipse of 1920.