《资治通鉴·唐纪·唐纪十一》
如今全国户口不及隋朝的十分之一，而服劳役的兄去弟归，道路相断。
今之户口不及隋之什一，而给役者兄去弟还，道路相继。
The number of registered households is now less than one-tenth of that of the Sui dynasty, and the "brother-goes-and-brother-returns" practice of alternating labor service has made the roads inaccessible. 