Authors: Wolf, D.
Published: 1995
Source: Pp. 567-569 in G. Maddox (ed.), Encyclopedia of Aging, Second Edition. New York, NY: Springer Publishing Company. Revised and updated version appears as pp. 609-611 in G. Maddox (ed.), Encyclopedia of Aging, Third Edition, Volume 1. (New York, NY: Springer Publishing Company, 2001).