Meri, Josef W. (2005). Josef W. Meri, ур. Medieval Islamic Civilization: An Encyclopedia. Psychology Press. стр. 510. ISBN0-415-96690-6. Приступљено 2011-11-28. „This called for the employment of engineers to engage in mining operations, to build siege engines and artillery, and to concoct and use incendiary and explosive devices. For instance, Hulagu, who led Mongol forces into the Middle East during the second wave of the invasions in 1250, had with him a thousand squads of engineers, evidently of north Chinese (or perhaps Khitan) provenance.”
Meri, Josef W.; Jere L. Bacharach (2006). Josef W. Meri, Jere L. Bacharach, ур. Medieval Islamic Civilization: L-Z, index. 2 of Medieval Islamic Civilization: An Encyclopedia (illustrated изд.). Taylor & Francis. стр. 510. ISBN0-415-96692-2. Приступљено 2011-11-28. „This called for the employment of engineers to engage in mining operations, to build siege engines and artillery, and to concoct and use incendiary and explosive devices. For instance, Hulagu, who led Mongol forces into the Middle East during the second wave of the invasions in 1250, had with him a thousand squads of engineers, evidently of north Chinese (or perhaps Khitan) provenance.”
doi.org
Vaziri, Mostafa (2012). „Buddhism during the Mongol Period in Iran”. Buddhism in Iran: An Anthropological Approach to Traces and Influences (на језику: енглески). Palgrave Macmillan US. стр. 111—131. ISBN9781137022943. doi:10.1057/9781137022943_7.