Online version of a print book

Most print books are now also available in the electronic form (e.g., in online libraries, book stores, etc.).

Ebooks (for electronic devices)

These books are available for downloading and reading through electronic devices and may have additional features that help enrich the reading experiences.

Author(s). (Year). Title of the book [Additional note]. Retrieved from http://www ...

Author(s). (Year). Title of the book [Additional note]. doi number.

Horowitz, D. (2017). Big agenda: President Trump's plan to save America [Kindle edition]. Retrieved from https://www.amazon.com/Big-Agenda-President-Trumps-America-ebook/dp/B01N4FHVDE/ref=sr_1_3?s=digital-text&ie=UTF8&qid=1485118394&sr=1-3

Mathijs, E., & Sexton, J. Cult cinema: An introduction (1st ed.) [Kindle edition]. doi:10.1002/9781444396447.

Traditional ebooks

These books can be accessed and read online through a website (a book portal, an online library, etc.).

Author(s). (Year). Title of the book. Retrieved from http://www ...

Maxwell, W. (1946). The heavenly tenants. Retrieved from http://digital.library.upenn.edu/women/maxwell/tenants/tenants.html

Basic rules

Author(s). (Year). Title of the book [Additional note]. Retrieved from http://www...

Beschloss, M., & Talbott, S. (1993). At the highest levels: The inside story of the end of the Cold War [Kindle edition]. Retrieved from https://www.amazon.com/At-Highest-Levels-Inside-Story-ebook/dp/B01J9AGM3K/ref=sr_1_15?s=digital-text&ie=UTF8&qid=1485122235&sr=1-15

Most of the elements overlap with those for print books, except that:

after the italicized title, the electronic format of the book is indicated in square brackets in place of location and name of publisher (e.g., Kindle edition, if the book is to be downloaded and read through a Kindle e-reader)
the information on the electronic format can be omitted if the book was not intended to be accessed through an electronic device
Retrieved from is used to provide the URL of the website through which the book can be found and retrieved (no date is provided for when the book was accessed and retrieved online)
as an alternative to the URL, a doi number assigned by the publisher can be given (where applicable)
the book's edition (e.g., 1st, 2nd, 3rd ed.) can be indicated in parentheses to show which of its print versions is offered in the digitized form (where applicable).