1. Federal Interagency Forum on Aging Related Statistics. http://www.agingstats.gov/agingstatsdotnet/Main_Site/Data/2008_Documents/Health_Status.pdf
2. Population Division. http://www.un.org/esa/population/publications/worldageing19502050/pdf/90chapteriv.pdf
3. Caring for an aging population;Winker;Call for papers,2010
4. National Academy on an Aging Society. http://www.agingsociety.org/agingsociety/pdf/Caregiving.pdf