Q. OpenStax e-textbook. How do I cite it?
OpenStax is a little different from your typical e-textbook. You're looking at a group author instead of a person.
Your reference will follow this pattern:
Author. (Year). Title. Publisher. http://URL
Here's an example citation for the Anatomy & Physiology textbook:
OpenStax College. (2013). Anatomy & physiology. OpenStax. http://cnx.org/content/col11496/latest/
OpenStax College is your group author. The copyright date (year) and the URL can be found on the copyright page of the PDF of the e-textbook.
If you have a link to the e-textbook in your class, and it opens in your browser (and not in a PDF), then the copyright date may be different. To find the correct copyright date for the web-based version of the textbook, go to the Table of Contents area, select "Preface" and then look for the "Attribution" section (it may be all the way at the bottom of the page). The copyright date should be located there.