1 2 3 Dynamics, Theory and Applications by T.R. Kane and D.A. Levinson, 1985, pp. 90-99: Free download ↑ Physics for Engineering by Hendricks, Subramony, and Van Blerk, page 148, Web link ↑ Engineering Mechanics: Equilibrium, by C. Hartsuijker, J. W. Welleman, page 64 Web link 1 2 3 Augustus Jay Du Bois (1902). The mechanics of engineering, Volume 1. Wiley. p. 186.