1. Notation, 1965 Symposium on Elastohydrodynamic Lubrication, Proc. Institute of Mechanical Engineers, Vol. 180, Pt 3B (1965?66) p. 4.
2. Research Group on Wear of Engineering Materials of the European Organisation for Economic Co-operation and Development, Glossary of Terms and Definitions in the Field of Friction, Wear and Lubrication (Organisation for Economic Co-operation and Development, Paris, 1969) p. 53.
3. P.M. Ku, ASLE Trans. 19 (1976) 239.
4. K.C. Ludema, Wear 100 (1984) 315.
5. S.C. Lee and H.S. Cheng, ASME J.Tribol. 113 (1991) 318.