APA (6th ed.):
ProCon.org. (2009, April 7). Historical Timeline. Retrieved from https://www.procon.org/historical-timeline/
[Editor's Note: The APA citation style requires double spacing within entries.]
Chicago (17th ed.):
ProCon.org, "Historical Timeline," ProCon.org. last modified April 7, 2009. https://www.procon.org/historical-timeline/.
MLA (8th ed.):
ProCon.org, "Historical Timeline." ProCon.org. 7 Apr. 2009, www.procon.org/historical-timeline/
[Editor’s Note: The MLA citation style requires double spacing within entries.]
Turabian (8th ed.):
ProCon.org. "Historical Timeline." ProCon.org. Last modified on April 7, 2009. Accessed January 15, 2021. https://www.procon.org/historical-timeline/