Three books provided the backbone for Part IV: (1) A Harmony of the Gospels for Historical Study (1904, 1932) by Stevens and Burton, which presents "an analytical synopsis of the four gospels"; (2) Atlas of the Historical Geography of the Holy Land (1915) by George Adam Smith, which contains every city, village, place and other geographical feature mentioned in Part IV; and (3) The Perfect Calendar for Every Year of the Christian Era (1926, 1927) by Henry Fitch, which allows one to find which day of the week any particular date fell on (e.g. that March 16, A.D. 1 was a Wednesday). Two Bible dictionaries—one by Hastings (1909), one by Smith (1870)—were regularly drawn from. Other much-used sources were the Life of Jesus books by Edersheim, Smith, Barton, Bowie, Murry, Wilson, and Fiske & Easton, as well as novels by Norwood and Poling. About thirty-five other books were also used, but in only a few papers at most. Papers 131, 160, 170 are specialized papers in which one source, used in no other paper in Part IV, was the dominant influence.