H. L. Humphries, PhD, B. K. Conrad, PhD, R. Berry, BA, S. Reed, and C. M. Jennings, BA, “Framing the Gift of Life: An Empirical Examination of Altruism, Social Distance and Material Incentives in Non-Directed Kidney Donor Motivation”, JNSW, vol. 31, pp. 19–26, Jul. 2009.