《旧唐书·本纪·卷十八》
宰相魏上奏曰 ：郑光凭借国舅的亲人关系，赐给他的田是可以的，如果免税就无法鼓励老百姓。 
宰相魏謩奏曰： 郑光以国舅之亲，赐田可也，免税无以劝蒸民。 
The prime minister Wei Shang said: Zheng Guang was given the land by virtue of his family relationship with the national uncle, and it is okay to give him the land, but if he is exempted from taxes, it will not encourage the common people.