The general format below refers to a book with more than three authors.
If you are dealing with a book that has more than three editors instead of authors, insert the names of the editors into the place where the authors' names are now, followed by a comma and the word "eds." without the quotation marks (as per the example). The rest of the format remains the same.
Either use the first author surname et al. or cite all names. Be consistent!
The Parenthetical Citation format should match the Works Cited entry, whether you are using et al. or all of the names of the authors or editors.
(Author Surname et al. page number)
(Author Surname, Author Surname, Author Surname, and Author Surname page
(Plag et al. 33)
(Plag, Braun, Lappe, and Schramm 33)