1. United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Highlights (ST/ESA/SER.A/423).
2. Sleep complaints among elderly persons: an epidemiologic study of three communities;Foley;Sleep,1995
3. Incidence and remission of insomnia among elderly adults: an epidemiologic study of 6,800 persons over three years;Foley;Sleep,1999
4. A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects;Rechtshaffen,1968
5. Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan;Ohayon;Sleep,2004