1. Nelson, H. R., Special Summer Conference on "Friction and Surface Finish", Massachusetts Institute of Technology, June 1940.
2. Moore, A. J. W., C.S.I.R. Lubrication and Friction Report No. 44 (unpublished).
3. Wulff, John, Trans. Amer. Inst. Mech. Eng., Iron and Steel Division, 295 (1941).
4. Benard, J., Lacombe, S. P., and Chaudron, G., "Journées des Etats de Surface" (Paris, October 1945).