1. National Sleep Foundation 2003 Sleep in America poll: Sleep in aging https://sleepfoundation.org/sleep-polls-data/sleep-in-america-poll/2003-sleep-and-aging 2003
2. Sleep complaints among elderly persons: An epidemiologic study of three communities;Foley;Sleep,1995
3. Assessment of sleep and circadian rhythm disorders in the very old: The Newcastle 85+ Cohort Study;Anderson;Age and Ageing,2013
4. Sleep disturbances in elderly subjects: An epidemiological survey in an Italian district;Bonanni;Acta Neurologica Scandinavica,2010