牛僧孺
In 802, then-19-year-old Yang Sifu passed the imperial examinations in the "Jinshi" class, and the next year, he passed a special examination for those with broad knowledge and grand speech. He was thereafter made a copyeditor (校書郎, "Xiaoshulang") at the Palace Library. As he passed the imperial examinations under the auspices of the chancellor Quan Deyu, as were Niu Sengru (after whom the Niu Faction would be named by later historians) and Li Zongmin, he developed deep friendships with them.