Format your citation like this if you are following APA style guidelines:
Author's Last Name, First Initial. (Year). In Title of Entry. Title of encyclopedia (Vol. number, pp. numbers). City of Publication: Name of Publisher.
Note that the title of the encyclopedia should be italicize and that only the first letter of the title of the encyclopedia should be capitalized. For example:
Jones, G. (2009). Communism. In The new encyclopedia britannica (Vol. 19, pp. 121-123). New York City: Penguin Press.
Format your citation like this if you are following MLA style guidelines:
"Article Title." Title of Encyclopedia. Edition of Encyclopedia. Year Published. Medium of Publication.
The title of the encyclopedia should be italicized.
Here is an example of a correct MLA citation:
"Communism." The New Encyclopedia Britannica. 5th ed. 2009. Print.
Format your citation like this if you are following Turabian/Chicago Style guidelines:
Author's First and Last Name, "Title of Article," in Title of Encyclopedia, Year of Edition.
The title of the encyclopedia should be italicized.
For example:
George Jones, "Communism," in The New Encyclopedia Britannica, 2009 ed.