  On November 18, 1915 Einstein reported to the Prussian Academy that the
perihelion motion of Mercury is explained by his new General Theory of
Relativity: Einstein found approximate solutions to his November 11, 1915 field
equations. Einstein's field equations cannot be solved in the general case, but
can be solved in particular situations. The first to offer such an exact
solution was Karl Schwarzschild. Schwarzschild found one line element, which
satisfied the conditions imposed by Einstein on the gravitational field of the
sun, as well as Einstein's field equations from the November 18, 1915 paper. On
December 22, 1915 Schwarzschild told Einstein that he reworked the calculation
in his November 18 1915 paper of the Mercury perihelion. Subsequently
Schwarzschild sent Einstein a manuscript, in which he derived his exact
solution of Einstein's field equations. On January 13, 1916, Einstein delivered
Schwarzschild's paper before the Prussian Academy, and a month later the paper
was published. In March 1916 Einstein submitted to the Annalen der Physik a
review article on the general theory of relativity. The paper was published two
months later, in May 1916. The 1916 review article was written after
Schwarzschild had found the complete exact solution to Einstein's November 18,
1915 field equations. Einstein preferred in his 1916 paper to write his
November 18, 1915 approximate solution upon Schwarzschild exact solution (and
coordinate singularity therein).
