1. U. S. Census Bureau, Population Projections Branch Aging in the Americas into the XXI century 1998
2. Population Division, United Nations World population ageing: 1950-2050 United Nations 2002 www.un.org/esa/populations/publications/worldageing19502050/
3. The coming acceleration of global population ageing;Lutz;Nature,2008
4. An address of the role of sepsis and antisepsis in medicine;Hunter;Lancet,1911