A United Nations University working paper titled "Urban Settlement" reviews the most commonly used data sources, and highlights the difficulties inherent in defining and measuring the size of urban versus rural populations.
联合国大学一篇题为《城市住区》（Urban Settlement） 的工作论文回顾了最常用的数据来源，并强调了定义和衡量城市与农村人口规模所带来困难。