Area code 531

a new area code. Say hello to the 656.. Tampa Bay Times. [2020-05-08]. （原始内容存档于2020-05-08） （英语）.  Rosenthal, Phil. Chicago's newest area code: 872. 芝加哥論壇報

Jersey. Accessed October 3, 2013. Area Code Lookup – NPA NXX for Montclair, NJ 互联网档案馆的存檔，存档日期April 28, 2021，., Area-Codes.com. Accessed October 3, 2013

(PDF)于2017-02-13）.  Montana Legislature. Classification of municipalities, Montana Code Annotated, (M.C.A.) 7-1-4124. Legislative Services Division. [2016-09-07]

Standards and Technology. [2013-07-21]. （原始内容存档于2013-04-23）.  EPA County FIPS Code Listing. US Environmental Protection Agency. [2013-07-21]. （原始内容存档于2012-10-08）

California Cities. [2014-03-08]. （原始内容存档于2013-10-21）.  California Government Code Sections 34502 and 56722. California Cities by Incorporation Date. California