1. Åkerstedt T, Fröberg JE, Friberg Y, Wetterberg L (1979) Melatonin excretion, body temperature and subjective arousal during 64 hours of sleep deprivation. Psychoneuro-endocrinology 4:219?225
2. Åkerstedt T, Gillberg M, Wetterberg L (1982) The circadian covariation of fatigue and urinary melatonin. Biol Psychiatry 17:547?553
3. American Psychiatric Association (1980) Diagnostic and statistical manual of mental disorders (3rd edn) (DSM-III). APA, Washington, DC
4. Aschoff J (1979) Circadian rhythms: general features and endocrinological aspects. In: Krieger DT (ed) Endocrine rhythms. Raven Press, New York, pp 1?61
5. Bjerner B, Holm A, Swensson A (1955) Diurnal variation in mental performance. Br J Int Med 12:103?110