62.查理大帝:James E. Alleman and Brooke T. Mossman, “Asbestos Revisited.” Scientific American 277.1 (1997): 70-75.
63.希罗多德:Timothy F. Garrard, “Myth and Metrology: The Early Trans-Saharan Gold Trade.” Journal of African History 23.4 (1982): 443-461.
64.“双方都是非常诚实的”:Herodotus, The Histories, trans. Aubrey de Sélincourt (1996): 4: 277.
65.“希望买方加价”:al-Mas‘ūdī in Levtzion and Hopkins, ed., Corpus of Early Arabic Sources for West African History, 32; al-Mas‘ūdī, Murūj al-dhabhab, Volume 2, ed. ‘Abd al-H3amīd (1958): 261.