1. Friedrich Bock, “Deutsches Handwerk im Mittelalter”, Leipzig, 1935; W. Treue et al; “Das Hausbuch der Mendelschen Zwülfbroderstiftung zu Nürnberg”, München, 1965; H. Ohlhaver, “Der Germanische Schmied und sein Werkzeug”,Hamburger Schriften zur Vorgeschichte und Germanischen Frühgeschichte, 1939,2, 75–80
2. Theophilus, “De Diversis Artibus”, Book III, Chapter VIII. For translations into English see C. R. Dodwell, “Theophilus: The Various Arts”, London, 1961, p. 68, J. G. Hawthorne and C. S. Smith, “On Divers Arts: The Treatise of Theophilus”, Chicago, 1963, pp. 87–89
3. R. P. Hommel, “China at Work”, New York, 1937 (reprinted M.I.T. Press, Cambridge, Massachusetts, 1969), pp. 25–27
4. H. E. Wulff, “The Traditional Crafts of Persia”, M.I.T. Press, Cambridge, Massachusetts, 1966, pp, 42–46
5. J. Needham, “Science and Civilisation in China: Vol. IV, Physics and Physical Technology: Part II, Mechanical Engineering”, Cambridge, 1965, p. 59