1. Abell, R. F. (1977). Reprint 770019 Society of Automotive Engineers, Warrendale, Pa.
2. Ali, M.S. and Thomas, M. P. (1964). Proc. Symp. Gear Transm. Oils and Their Testing Vol. V, p. 1. Institute of Petroleum, London.
3. “Mechanical Wear’;Almen,1948