1. McVittiE, G.C.: General Relativity and Cosmology, London: Chapman and Hall, (1956) p. 85.
2. WhittakeR, E. T.: Analytical Dynamics, Cambridge: University Press, 3rd. ed. (1927) Sec. 47.
3. Notations as in W. M. Smart: Celestial Mechanics, London: Longmans, Green (1953) p. 21.
4. Smart, W. M.: loc. cit., p. 220.
5. Smart, W. M.: loc. cit., p. 69.