1. W. E. CAMPBELL and U. B. THOMAS: Proc. 3rd Int. Research Symp. on Electric Contact Phenomena, Orono, ME, 1966, University of Maine, 83.
2. Tarnish Studies
3. W. H. ABBOTT Proc. 33rd Int. IEEE/Holm Conf. on Electrical Contacts, Chicago, IL, September 1987.