Please note: Wikipedia is a good resource for learning about a topic, but it is usually not an acceptable source to cite in a paper or research project. This is due to the fact that it can be very unreliable and is not considered a reputable source.
Title of entry. (Year, Month Day). In Wiki Name. http://xxxxx
Constitution of the United States. (2019, October 7). In Wikipedia. https://en.wikipedia.org/w/index.php?title=Constitution_of_the_United_States&oldid=920036236
As in-text citation:
("Constitution," 2019).
Note: Provide the link to the archived version of the entry you use. Click View history and the time/date corresponding to the entry version you used.
Greek mythology. (2008). In Citizendium. Retrieved August 12, 2009, from http://en.citizendium.org/wiki/Greek_mythology
As in-text citation:
("Greek Mythology," 2008).
Note: If there is no link to an archival version of the page, provide the retrieval date that you accessed the entry.
Source: Publication Manual, 10.3 (example 49)
This kind of texts is not handled well in a tool like Mendeley and is therefore recommended to do manually.