《新唐书·列传·卷八十八》
外族人来朝进贡，都在另外一份珍宝上写着 ：这是买柳公权的书法作品的。 
外夷入贡者，皆别署货贝曰： 此购柳书。 
When foreigners from other ethnic groups came to China to pay tribute, they always wrote on another piece of treasure: "This is purchased for the calligraphy of Liu Gongquan."