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3. Aleksandrov, V. M. and I. I. Vorovich, Prikl. Mat. Mekh. 28 (1964) 425 (in English translation).
4. Hannah, M., Quart. J. Mech. Appl. Maths., IV (1951) 94.
5. Koiter, W. T., Proc. Kon. Ned. Ak. Wet., Amsterdam, B 57 (1954) 558.