Sources
* {{cite web, url=http://www.laogai.it/wp-content/uploads/2009/06/laogai-handbook.pdf , title=Laogai Handbook 2007-2008 , date=October 2008 , isbn=978-1-931550-25-3 , format=PDF , language=Chinese, English , publisher=Laogai Research Foundation , location=Washington, D.C. , access-date=24 May 2017 , pages=81–92 Buildings and structures in Gansu Gansu