Ebrey & Walthall 2014 harvnb error: no target: CITEREFEbreyWalthall2014 (help), [1]，第171頁，載於Google圖書: Liao forces invaded Goryeo territory in 993. Instead of pushing for total victory, the Khitans negotiated a peace that forced Goryeo to adopt the Liao calendar and end tributary relations with Song (a violation of King Taejo’s testamentary injunction never to make peace with the Khitan)."
