1. A. Sommerfeld: Electrodynamics (Academic, New York 1952) p. 286
2. A. Sommerfeld: Mechanics of Deformable Bodies (Academic, New York 1950) p. 132
3. L. D. Landau, E. M. Lifshitz: Electrodynamics of Continuous Media (Pergamon, Oxford 1960) p. 208
4. R. P. Feynman, R. B. Leighton, M. Sands: The Feynman Lectures on Physics, Vol. 2 (Addison-Wesley, Reading, MA 1975) p. 17–2
5. C. Møller: The Theory of Relativity (Clarendon, Oxford 1972) p. 214