1. L. I. Averkova, ?Finding the natural frequencies of hollow ribbed shells using the properties of orthogonal functions of a discrete argument,? in: Theoretical Investigations of Structures [in Russian], Moscow (1977), pp. 9?15.
2. L. G. Agenosov, ?On free vibrations of ribbed conical shells,? Tr. Tyumen. Ind. Inst.,40, 174?179 (1974).
3. I. Ya. Amiro and V. A. Zarutskii, ?Experimental and theoretical determination of the natural frequencies of reinforced cylindrical shells,? Prikl. Mekh.,13, No. 10, 6?13 (1977).
4. I. Ya. Amiro and V. A. Zarutskii, Methods of Shell Design. Vol. 2. Theory of Ribbed Shells [in Russian], Naukova Dumka, Kiev (1980).
5. I. Ya. Amiro and V. G. Palamarchuk, ?Free vibrations of a ribbed cylindrical shell with a mass on springs?, Probl. Prochn., No. 5, 83?85 (1979).