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Needham, J. "Astronomy in Ancient and Medieval China 30 Kasım 2020 tarihinde Wayback Machine sitesinde arşivlendi.". Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 276, No. 1257, The Place of Astronomy in the Ancient World (May 2, 1974), pp. 67 –82. Accessed 9 Oct 2012.
