1. Are morning headaches part of obstructive sleep apnea syndrome?;Aldrich;Archives of Internal Medicine,1990
2. American Academy of Sleep Medicine. The international classification of sleep disorders revised: diagnostic and coding manual. Rochester, Minnesota: American Academy of Sleep Medicine; 1997.
3. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed. (DSM-IV). Washington: The American Psychiatric Association, 1994.
4. Daytime sleepiness and napping amongst the elderly in relation to somatic health and medical treatment;Asplund;Journal of Internal Medicine,1996
5. Insomnia in central Pennsylvania;Bixler;Journal of Psychosomatic Research,2002