1. Kappus, R., Twisting failure of centrally loaded opensection columns in the elastic range, English Translation. NACA Technical Memorandum No. 851.
2. Wagner, H., Torsion and buckling of open sections, English Translation. NACA Technical Memorandum No. 807.
3. The normal modes of vibrations of beams having noncollinear elastic and mass axes;Garland;Journal of Applied Mechanics,1940
4. Torsional and flexural buckling of bars of thin-walled open section under compressive and bending loads;Goodier;Journal of Applied Mechanics,1941
5. Eigenschwingungen von geraden Staben mit dunnwandigen und offenen Querschnitten;Federhofer,1947