1. W. J. M. Rankine: Institution of Civil Engineers (British), Minutes of Proceed- ings, vol. 3, p. 105, 1843.
2. C. Hood:ibid, vol. 2, p. 180, 1842.
3. A. Wöhler:Z. Bauw., 1858, vol. 8, p. 642;ibid, 1860, vol. 10, p. 583;ibid, 1863, vol. 13, p.233;ibid., 1866, vol. 16, p. 67;ibid., 1870, vol. 20, p. 74.
4. A. Wöhler (translated and edited anonymously):Engineering, 1867, vol. 4, p. 160; ibid., 1871, vol. 11, pp. 199, 221, 243, 261, 299, 327, 397, and 439.
5. W. Fairbairn:Phil. Trans. Roy. Soc., 1864, vol. 154, p. 211.