1. E. Cumming and W.E. Henry. Growing Old The Process of Disengagement (Basic Books, New York, 1961).
2. L.L. Carstensen, Motivation for social contact across the life span: A theory of socioemotional selectivity, in Nebraska Symposium on Motivation: Vol. 40. Developmental Perspectives on Motivation, J. Jacobs, Ed. (University of Nebraska Press, Lincoln, 1993).