《资治通鉴·唐纪·唐纪四十九》
元友直检查各道在税收以外加征的财物，并将它们全部上缴户部。以后这种做法便成了固定的制度，每年要在税收以外缴纳一百余万缗、斛，百姓难以忍受这种索求。
元友直句检诸道税外物，悉输户部，遂为定制，岁于税外输百馀万缗、斛，民不堪命。
Yuan Youzhi audited the property levied in addition to taxes in various Daos and handed them all over to the Ministry of Revenue. Later, this practice became a fixed system. More than 1 million guan of taxes and hu were to be paid each year. The people could not bear this kind of demand.