Houghton P S, . (1961). Gears Spur Helical Bevel and Worm. London: Technical Press Ltd.
Houghton P S, . 1961. Gears Spur Helical Bevel and Worm. London: Technical Press Ltd.
Houghton P S, . Gears Spur Helical Bevel and Worm. London: Technical Press Ltd. 1961.