===Old sources=== 

 * Jacques Gernet (1972). "A History Of Chinese Civilization". Cambridge University Press. ISBN 0-521-24130-8 
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 * Wittfogel K.A., Feng Chia-Sheng History of Chinese Society. Liao (907-1125). Philadelphia, 1949 (Transactions of the American Philosophical Society, new series, 36) 
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 * Wang Gungwu, "The Rhetoric of a Lesser Empire: Early Sung Relations with Its Neighbors" in Rossabi, Morris, ed. China Among Equals: The Middle Kingdom and its Neighbors, 10th-14th Centuries. University of California Press, 1983, pp. 47–65.