Hashemi, S. M., and M. J. Richard. “A Bernoulli-Euler Stiffness Matrix Approach for Vibrational Analysis of Linearly Tapered Beams”. Canadian Acoustics, vol. 24, no. 3, Sept. 1996, pp. 87-87, https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1057.