1. Weber, W. (1852) Pogg. Ann., LXXXVII, 167.
2. Poisson, S. D. (1893) in Magnetic Induction in Iron and Other Methods (ed. J. A. Ewing), Electrician Publishing Company, London, p. 282.
3. Ampère, A. M. (1827) Theorie Mathematique des Phenomenes Electrodynamiques Uniquement Deduite de l’Experience, Reprinted by Blanchard, Paris (1958).
4. Ewing, J. A. (1893) Magnetic Induction in Iron and Other Metals, The Electrician Publishing Company, London.
5. Weiss, P. (1906) Compt. Rend., 143, 1136.