Write the authors' names, followed by a period. If there are only two authors, then you need to list both in the same order that their names appeared on the title page. The first author's name should be listed last name, then first name and subsequent authors' names will be listed with the first name first. The last in the list will be joined to the list by the word "and." For example, if the book was written by Ann Joelson and Liddy Bettly, then your citation would read, thus far: Joelson, Ann, and Liddy Bettly. If there are more than two authors, you have the option of simply writing "et al." after the first author's name. If Ann Joelson, Liddy Bettly and Jacob Hurley had written the book, the citation would look like this: Joelson, Ann, et al.