Title of Online Reference Work, "title of entry," Date, URL.
2. Britannica Academic, "Chinook," last updated April 7, 2015, https://academic.eb.com/levels/collegiate/article/Chinook/82174.
If author is given:
2. First Name Last Name, "Title of Entry." In Title of Reference Work, editor. Publisher, date. URL.
2. Karen Sawislak. "Fire of 1871." In Encyclopedia of Chicago, edited by Janice L. Reiff, Ann Durkin Keating, and James R Grossman. Chicago Historical Society, 2005. http://www.encyclopedia.chicagohistory.org/pages/1740.html.