1. R.P. Feynman, R.B. Leighton and M. Sands, The Feynman Lectures on Physics, Addison-Wesley, Reading, MA, 1963.
2. C. DeWitt-Morette and D. Rickles, The Role of Gravitation in Physics, Report from the 1957 Chapel Hill Conference, Edition Open Access, Berlin, 2011.
3. R. P. Feynman, Quantum theory of gravitation, Acta Phys. Polon. 24 (1963), 697-722.
4. C. Will, Was Einstein Right? Putting General Relativity to the Test, Oxford University Press, Oxford, 1986.
5. C. Will, The renaissance of general relativity, in P. Davies (ed.), The New Physics, Cambridge University Press, Cambridge, 1989.