1. J. J. Thomson, Phil. Mag. (5) 47, 253, 1899.
2. Conduction of Electricity through Gases, Cambridge 1903, (Kap. III).
3. E.v. Schweidler, Wien. Ber. 108, 899, 1899.
4. E.v. Schweidler, Wien. Ber. 113, 1120, 1904.
5. E. Rutherford, Phil. Mag. (5) 47, 109, 1899.