Semantics of sleep.
D001921:Brain / Q000502:physiology; D001923:Brain Chemistry; D005060:Europe; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D049690:History, Ancient; D006801:Humans; D009290:Narcolepsy / Q000266:history; D010827:Physiology / Q000266:history; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000266:history; D009626:Terminology as Topic