《资治通鉴·唐纪·唐纪二十七》
唐玄宗对宰相们说： 每当朕读书遇到疑难问题的时候，都找不到一个可以请教的人；你们可以挑选儒学之士，每天入宫侍读。 
上谓宰相曰： 朕每读书有所疑滞，无从质问；可选儒学之士，日使入内侍读。 
Emperor Xuanzong of the Tang dynasty said to his prime ministers, "Whenever I encounter a difficult question while studying, I cannot find anyone to ask. You can select men of Confucianism to accompany me in the palace every day to read."