ReferenceBennett, M., Bradbury J., Devries, K., Dickie, I., Jestice, PG. (2013). Fighting Techniques of the Medieval World AD 500 - AD 1500: Equipment, Combat Skills and Tactics (pp 192-193). Sterling Publishing.
Needham, J., Yates, R. D. S. (1988). Science and civilisation in China. Vol. 5, Chemistry and chemical technology. Part 6, Military Technology: Missiles and Sieges (pp 142-181). Cambridge [England]: Cambridge University Press.
Turnbull, S. (2004). Siege Weapon of the Far East (pp 20-22). Osprey Publishing Ltd.