Found in a review by Gary Will’s of Taylor Branch’s At Canaan’s Edge: America in the King Years, 1965-1968 in the NYRB (2006-04-06, p. 20):
It is amazing how Branch can marshal so much material along so many tracks, moving it ahead stage by stage in coordination with King's actions. The I saw Branch in a three-hour television interview with C-SPAN and learned part of his secret. He showed the interviewer his computer with its expertly programmed chronological record of all the information he had acquired from so many sources -- over 17,000 items arranged year by year, day by day. The book probably could not have been written -- surely not in so relatively short a time -- without the computer.