(the University of Michigan)John Merton Patrick. Artillery and warfare during the thirteenth and fourteenth centuries. Utah State University Press, 12. o. (1961). Hozzáférés ideje: 2011. november 28. „The Mongols invaded the Russian steppes at this time, reaching the Crimea before turning back at the Khan's orders. The youngest son of Genghis, Tului, was given the special task of destroying walled cities during this campaign, employing the Chinese engines”
