If a work, such as a website, does not include page numbers, then omit this portion of the in-text citation.
Example:
Marx used “class” in “two different ways” (Calvert).
Some sources—like ebooks—employ location indicators other than page numbers. If your work is divided into stable sections like chapters, those sections may be cited. Do not use the location numbers used within an ebook as the locations are often specific to that app or device.
Example:
Marx used “class” in “two different ways” (Calvert, ch. 4).