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3. Bleich F, Bleich H. Bending, torsion, and buckling of bars composed of thin walls. In: Prelim. pub. 2nd congress of international association for bridge and structural engineers, english ed.; 1936. p. 871.
4. Twisting failure of centrally loaded open-section columns in the elastic range;Kappus;Luftfahrtforschung,1937
5. Thin-walled elastic beams;Vlasov,1963