Gray, J. O.; Caldwell, D. G. (ed.): 'Advanced Robotics and Intelligent Machines' (Control, Robotics and Sensors, 1996) DOI: 
IET Digital Library, https://digital-library.theiet.org/;jsessionid=3qrakf4j8d0aa.x-iet-live-01content/books/ce/pbce051e