He then joined the religion faculty of Emmanuel Missionary College, while continuing his doctoral work at the University of Chicago. He obtained a PhD degree in biblical archaeology in 1943. His doctoral dissertation, The Chronology of the Kings of Judah and Israel,[1] was later expanded and published as The Mysterious Numbers of the Hebrew Kings[2] which is widely regarded as an important work on the chronology of Hebrew kings.[3] He traveled extensively throughout the Middle East in the course of his research.