Aurell, J.& Elmqvist, D.(1985): Sleep in the surgical intensive care unit; Continuous polygraphic recording of sleep in nine patients receving postoperative care, Br Med J, 290(6474), 1029-1032.
Cole, R. J., Kripke, D. F., Guren, W., et al (1992): Technical note automatic sleep/wake indentification from wrist activity, Sleep, 15(5), 461-469.