Lee, Injae; Miller, Owen; Park, Jinhoon; Yi, Hyun-hae (2014). Korean History in Maps. Cambridge University Press. pp. 30, 49. ISBN9781107098466. Retrieved 1 February 2016.
Kim, Jinwung (5 November 2012). A History of Korea: From "Land of the Morning Calm" to States in Conflict. Indiana University Press. p. 36. ISBN978-0253000781. Retrieved 15 July 2016. "Because Pyongyang was located in the vast, fertile Taedong River basin and had been the center of advanced culture of Old Chosŏn and Nangnang, this move led Koguryŏ to attain a high level of economic and cultural prosperity."
Kim, Hyun Jin (2013). The Huns, Rome and the birth of Europe (1. publ. ed.). Cambridge: Cambridge University Press. p. 61. ISBN9781107009066. Retrieved 2 February 2016. The Khitans, although descended from the Xianbei and presumably inheriting their martial and political traditions, were for a long time a weak people who were subjected successively to the Rouran, Koguryo, Sui-Tang China and then most importantly the Gokturk.
