1. Biezeno, C. B., and Grammel, R. Technische Dynamik, 1st ed., Springer, Berlin, 1939.
2. Engesser, F. Z. Architek u. Ing. Verein Hannover, Vol. 35, pp. 733–774, 1899.
3. Lord Rayleigh. Theory of Sound, 2nd ed., Vols. I and II, Macmillan, London, 1892 and 1896.
4. Maxwell, J. C. Phil. Mag., Vol. 27, p. 294, 1864.
5. Mohr, O. Z. Arch. u. Ing. Verein Hannover, 1874, p. 509, and 1875, p. 17.