1. J. Algermissen, Ann. d. Phys. (4) 19, 1007; 1906.
2. J. E. Almy, Phil. Mag. (6) 16, 456; 1908.
3. J. B. Baille, Ann. chim. phys. (5) 25, 486; 1882.
4. J. B. Baille, Ann. chim. phys. (5) 29, 181; 1883.
5. E. Bichat u. R. Blondlot, Journ. de phys. (2) 5, 457; 1886.