1. Hu, W. C. L. "A Survey of the Literature on the Vibrations of Thin Shells, Tech. Rep. No. 1, Contract No. NASr-94(06), Southwest Research Institute (1964).
2. Hu, W. C. L. "Free Vibrations of Conical Shells, I' NASA TN D-2666 (1965).
3. Federhofer, K. "FreeVihrations of Conical Shells, 'I NASA TT F-8261 (1962). Translated from hgr.Arch., 9 (1938).
4. Grigolyuk, E. I. "Small Oscillations of Thin Resilient Conical Shells, 'I NASA TT F-25 (1960). Translated from Izves. Akad. Nauk SSSR, 0.T. D., No. 6 (1956).
5. Herrmann, G., and Mirskv, I. "On Vibrations of Conical Shells, 'I Journal of Aerospace Science, 2,pp. 451-458 (1958).