1. Thomas, W.M, et al., “Improvements Relating to Friction Welding”. European Patent Specification 0 615 480 (PCT/GB92/02203). The Welding Institute, Cambridge, 27 Nov. 1992.
2. Midling Ole, T. & Johansen Helge, G., “Production of Wide Aluminium Profiles by Solid-State Friction Stir Welding”. 6th International Conference on Extrusion Technology, ET96, Chicago, May 1996, pp. 373–378.