Ford Tractor Conversions is an excellent book by Author Stuart Gibbard with detailed histories of County tractors, Doe, Chaseside, Muir-Hill, Matbro and Bray who were all well-known British companies and leaders in their own fields of engineering design and innovation, each producing successful ranges of agricultural, earthmoving or construction machinery. Linked by their extensive use of the Ford tractor skid units as a basis for their machines, these companies also pioneered the development of the four-wheel-drive agricultural tractor in Britain.