Colin S. Gordon Electronic References Below is a loosely-categorized collection of links to CS textbooks in a variety of areas that are freely available online, usually because they are one of the following: An open textbook (such as PLAI, SF, or the HoTT book) An older book that is out of print, for which the copyright has returned to the original author(s) (such as TTFP) An author’s own preprint or draft of a textbook. This includes cases where the author has made special arrangements with a publisher to host an electronic copy of a published text on their