Kaplan RS, Witkowski M, Abbott M, Guzman AB, Higgins LD, Meara JG, Padden E, Shah AS, Waters P, Weidemeier M, Wertheimer S, Feeley TW. Using time-driven activity-based costing to identify value improvement opportunities in healthcare. J Healthc Manag. 2014; 59(6):399-412.