Macri, M. ., J. . Tichy, and S. . De. “On the Application of the Method of Finite Spheres to Problems in Tribology”. European Journal of Computational Mechanics, vol. 14, no. 2-3, July 2005, p. 339 to 366, https://journals.riverpublishers.com/index.php/EJCM/article/view/2245.