《管子·乘马数》
管种回答说： 对郡县上等土地，掌握它相当数量的粮食。中等土地掌握它相当数量的粮食。
管子对曰： 郡县上臾之壤守之若干，间壤守之若干，下壤守之若干。
Guan Zhong replied: For the best land in the county, keep a certain amount of grain in reserve; for the medium land, keep a certain amount of grain in reserve; for the poor land, keep a certain amount of grain in reserve. In this way, the levy is determined according to the quality of the land, so the people will be stable; by selling grain to the poor and making up for the shortfall, the people will also be satisfied with the monarch.