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[2] J. Singer: Buckling of orthotropic and stiffened conical shells. Collected papers on instability of shell structures. N. A. S. A. T. N. D - 1510, p. 463.

[3] J. Singer R. Fersh-Scher: Buckling of orthotropic conical shells under external pressure. Aeronautical Quarterly XV (1964), 151-168.

[4] S. Timoshenko S. Woinowsky-Krieger: Theory of plates and shells. McGraw Hill, New York, 1959.