1. W. L. Roberts, ?Resistance variation during spot welding?,Welding Journal,30, pp. 1004?1019, November 1951.
2. B. Irving, ?Ford Motor Co's Hilligoss speaks out about welding?,Welding Journal,73, pp. 59?61, August 1994.
3. B. Hass, ?Resistance spot welding ? the key to quality?,Welding and Metal Fabrication, pp. 166?170, May 1992.
4. C. L. Tsai, O. A. Jammal, J. L. Papritan and D. W. Dickinson, ?Modelling of resistance spot weld nugget growth?,Welding Journal ? Research Supplement,71, pp. 47?54, 1992.
5. H. S. Chang, Y. J. Cho and S. G. Choi, ?A proportional-integral controller for resistance spot welding using nugget expansion?,Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME,111, pp. 332?336, June 1989.