  In December 1911, Max Abraham published a paper on gravitation at the basis
of which was Albert Einstein's 1911 June conclusion about a relationship
between the velocity of light and the gravitational potential. In February
1912, Einstein published his work on static gravitational fields, which was
based on his 1911 June theory. In March 1912, Einstein corrected his paper, but
Abraham claimed that Einstein borrowed his equations; however, it was actually
Abraham who needed Einstein's ideas and not the other way round. Einstein
thought that Abraham converted to his theory of static fields while Abraham
presumed exactly the opposite. Einstein then moved to Zurich and switched to
new mathematical tools. He examined various candidates for generally covariant
field equations, and already considered the field equations of his general
theory of relativity about three years before he published them in November
1915. However, he discarded these equations only to return to them more than
three years later. Einstein's 1912 theory of static fields finally led him to
reject the generally covariant field equations and to develop limited generally
covariant field equations.
