The letter is accepted as genuine in Petech, Luciano (1990), p. 9, and Van Schaik, Sam (2011) Tibet: A history. New Haven & London: Yale University Press, p. 77. Jackson, David P. (1987) [3] argues that it may be authored long after Sakya Paṇḍita's death.
According to Townsend, Dominique (2010) "Sakya Pandita Kunga Gyeltsen", [1] this took place later, in 1240.
According to Norbu, Thubten Jigme and Turnbull, Colin (1969) Tibet: Its History, Religion and People. Chatto & Windus. Reprint: Penguin Books (1987), p. 195, and Townsend, Dominique, "Sakya Pandita Kunga Gyeltsen" (2010), [2], Sakya Paṇḍita, with the help of his nephew, Phagpa, adapted the Uighur script so that the Buddhist Scriptures could be translated into Mongolian which, until that time, was an unwritten language. This is not clear from more detailed studies which indicate that the new script was developed much later, in the 1260s.
Powers, John (2017). The Buddha party : how the people's Republic of China works to define and control Tibetan Buddhism. New York: Oxford University Press. pp. Appendix B, p. 15. ISBN9780199358151. OCLC947145370.
