References
Goodstein, D. L. and Goodstein, J. R. (1996) Feynman's Lost Lecture, The Motion of Planets around the Sun, London: Vintage Books.
Feynman, R., Leighton, R. and Sands, M. (2005) The Feynman Lectures on Physics, 2nd ed., Volume 1, Addison Wesley, USA.