《资治通鉴·唐纪·唐纪六十二》
庚辰，李德裕上朝向武宗谢恩。他对武宗说： 治理天下的关键，在于辨别群臣中谁是邪恶的小人，谁是正直的君子。
庚辰，德裕入谢，言于上曰： 致理之要，在于辩群臣之邪正。
On Gengchen, Li Deyu went to court to express his thanks to Emperor Wuzong. He said to Emperor Wuzong: The key to governing the country lies in distinguishing between evil and upright people among the ministers.