Many more materials related to sleep are listed here.

Aronoff, M. S. (1991). Sleep and its secrets: The river of crystal light. New York: Insight Books.

Carskadon, M. A. (1993). Encyclopedia of sleep and dreaming. New York: Macmillan.

Dement, W. C. (1992). The sleepwatchers. Stanford, CA: Stanford Alumni Association.

Kryger, M. H., Roth, T., & Dement, W.C. (1989). Principles and practice of sleep medicine. Philadelphia: Saunders.

Stampi, C. (1992). Why we nap: Evolution, chronobiology and functions of polyphasic and ultrashort sleep. Boston: Birkhauser.