(原始内容存档于2017-04-30). Chris. Environmentalism in 1306. Environmental Graffiti. 2007. (原始内容存档于2008-07-25). Clearing the Air. The Surface Transportation Policy Project
movement in China in 1910s and 1920s. www.libcom.org. Libcom.org. 2014-06-04 [2014-10-09]. (原始内容存档于2022-06-10). 5 youths arrested for Toa Payoh graffiti case