Here is a link to a PDF file I found recently while googling for information on General Relativity. The author is apparently associated with Novgorod University in Russia. http://nifti.unn.ru/burlankov/burlankov.files/pdf/Bjern_e.PDF From the abstract Nearly 20 years before Einstein, Niels Bjern developed a theory of gravity based on what is today known as the equivalence principle - but naturally without invoking the ideas of the special relativity theory. An advocate of the absolute space concept, Bjern described the gravitational field in terms of the field of absolute velocities of an inertial space. He only used the ideas of general relativity to explain the precession of the perihelion of Mercury. The reason why Bjern's predictions and those of general relativity are identical are discussed. Bjern was a collaborator and student of Sophus Lie. His work was published in an obscure journal Archiv for Naturvidenskab.