1. Leonhardi Euleri Opera Omnia, Vol. X, ser. secundae, society for Natural Sciences of Switzerland, 1960, in particular the section of C. Truesdell's historical notes, p. 1638–1788, on the rational mechanics of flexible or elastic bodies.
2. J.L. Lagrange Sur la figure des colonnes, Miscellanea Taurinensia, Vol. V, 1970, (see p. 123–125).
3. J.B. Keller, The shape of the strongest column, Archives of Rational Mechanics and Analysis, Vol. 5 (1960), p. 275–285.
4. I. Tadjbakhsh and J.B. Keller, Strongest columns and isoperimetric inequalities for eigenvalues, J. of Applied Mechanics, Vol. 9, (1962), p. 159–164.
5. N. Olhoff, Optimal design against structural vibration and instability, Ph.D. Thesis, Technical University of Denmark, Dept. of Solid Mechanics, Lyngby, Denmark, November 1978.