This is a free textbook offered by Stitz and Zeager. According to the authors, "We are two college mathematics professors who grew weary of forcing our students to purchase expensive college algebra textbooks whose mathematical content has slowly degraded over the years. Our solution? Write our own. The twist? We made our college algebra book free and we distribute it as a .pdf file under the Creative Commons License. What’s more, the LaTeX source code is also available under the same license."