http://www.independent.co.uk/life-style/health-and-families/sleep-deprivation-insomnia-spoon-metal-tray-sleep-onset-latency-test-a7379631.html
http://www.independent.co.uk/life-style/health-and-families/sleep-deprivation-insomnia-spoon-metal-tray-sleep-onset-latency-test-a7379631.html