1. See: Transactions of the Faraday Society 33, pp. 1–282, 1937.
2. See F. London, The general theory of molecular forces, Trans. Farad. Soc. 33, p. 8. 1937; here also further references have been given.
3. This is illustrated by a diagram given by J. E. Lennard-Jones, Proc. Physic. Soc. London 43, p. 471, 1931.
4. See: J. C. Slater and J. G. Kirkwood, Physic. Review 37, p. 682, 1931.
5. See J. E. Lennard-Jones, l.c. and F. London, l.c