\begin{thebibliography}{10}

\bibitem{bleuler1950}
K.~Bleuler.
\newblock {\em Helv. Phys. Acta}, 23:567, 1950.

\bibitem{epstein1980}
R.~Epstein and I.~I. Shapiro.
\newblock Post-post-newtonian deflection of light by the sun.
\newblock {\em Phys. Rev. D}, 22(12):2947--2949, 1980.

\bibitem{feynman1964}
R.~P. Feynman, R.~B. Leighton, and M.~Sands.
\newblock {\em The Feynman Lectures on Physics}.
\newblock Addison-Wesley, 1964.

\bibitem{gupta1950}
S.~N. Gupta.
\newblock Theory of longitudinal photons in quantum electrodynamics.
\newblock {\em Proc. Phys. Soc.}, 63:681--691, 1950.

\bibitem{gupta1957}
S.~N. Gupta.
\newblock Einstein's and other theories of gravitation.
\newblock {\em Rev. Mod. Phys.}, 29:337--350, 1957.

\bibitem{landau1975}
L.~D. Landau and E.~M. Lifshitz.
\newblock {\em The Classical Theory of Fields}.
\newblock Pergamon Press, 1975.

\bibitem{pais1982}
A.~Pais.
\newblock {\em 'Subtle is the Lord...': The science and the life of Albert
  Einstein}.
\newblock Clarendon Press, 1982.

\bibitem{rosen1973}
N.~Rosen.
\newblock A bi-metric theory of gravitation.
\newblock {\em General Relativity Gravitation}, 4(6):435--447, 1973.

\bibitem{thirring1961}
W.~E. Thirring.
\newblock An alternative approach to the theory of gravitation.
\newblock {\em Ann. Phys. (U. S. A.)}, 16:96--117, 1961.

\bibitem{turyshev-2006-}
S.~G. Turyshev, M.~Shao, and K.~L. Nordtvedt.
\newblock Science, technology and mission design for the laser astrometric test
  of relativity, 2006.

\bibitem{weinberg1964}
S.~Weinberg.
\newblock Derivation of gauge invariance and the equivalence principle from
  lorentz invariance of the s-matrix.
\newblock {\em Phys. Let.}, (9):357--359, 1964.

\end{thebibliography}
