Add a set of parentheses just before the period of the sentence that includes the in-text citation. Include the textbook author's last name if the name is not mentioned directly in the sentence. If the textbook has multiple authors, include the last name of each author with a comma separating each one. Also include the word "and" before the final name.
Add the page numbers that you are referencing after the final author's name. This only includes the page numbers from which the particular reference is derived, not every page number used in your overall essay. The page number reference follows the name of the final author listed with no comma between the two.
Add a citation of the textbook volume, if applicable. Do so by writing the volume of the work in front of the page numbers you referenced, separated by a colon. For example, an in-text citation for the second volume of a textbook with multiple authors would be written as, "(Pynchon, Borges, and Faulkner 2:42-8)."