Kenneth Warren Chase (2003). Firearms: a global history to 1700 (illustrated edición). Cambridge University Press. p. 58. ISBN0-521-82274-2. Consultado el 28 de noviembre de 2011. «Chinggis Khan organized a unit of Chinese catapult specialists in 1214, and these men formed part of the first Mongol army to invade Transoania in 1219. This was not too early for true firearms, and it was nearly two centuries after catapult-thrown gunpowder bombs had been added to the Chinese arsenal. Chinese siege equipment saw action in Transoxania in 1220 and in the north Caucasus in 1239-40.»
