1. P. Langevin: J. Phys. (Paris) 4, 678 (1905);
2. P. Langevin: Ann. Chim. Phys. 5, 70 (1905)
3. P.Weiss: J. Phys. Radium 6, 661 (1907)
4. J. H. Van Vleck: Theory of Electric and Magnetic Susceptibilities (Oxford Univ. Press, Oxford 1932 )
5. W. Heisenberg: Z. Phys. 49, 619 (1928)