Diana Hacker’s A Pocket Style Manual features three popular formats: MLA, APA, and Chicago. Of the three listed, Chicago is most common for history and the humanities. For special instructions on how to cite Internet sources, see Hacker’s A Pocket Style Manual, Fourth Edition, pages 174-175. You can, of course, always consult The Chicago Manual Style, 15th ed (located at the Reference Desk). For Internet sources, see Chapter 17. The Reference Staff has created handouts on the three popular styles.