A.D.A.M. Medical Encyclopedia (from MedlinePlus)
"The A.D.A.M. Medical Encyclopedia includes over 4,000 articles about diseases, tests, symptoms, injuries, and surgeries. It also contains an extensive library of medical photographs and illustrations."  Part of MedlinePlus.
Gale Encyclopedia of Alternative Medicine
"Information on alternative and complementary medical practices, including reflexology, acupressure, acupuncture, chelation therapy, kinesiology, yoga, chiropractic, Feldenkrais, polarity therapy, detoxification, naturopathy, Chinese medicine, biofeedback, Ayurveda, and osteopathy."
Gale Encyclopedia of Cancer
"Survey of 120 cancers, cancer drugs, traditional and alternative treatments, side effects and diagnostic procedures."
Gale Encyclopedia of Medicine
"Includes information on more than 1,600 medical disorders and concepts. Each article includes in-depth discussion of causes, symptoms, diagnosis, treatments, procedures, and other related topics."
Gale Encyclopedia of Neurological Disorders
"Provides in-depth coverage of neurological diseases and disorders, including stroke, multiple sclerosis, Parkinson disease, Tourette Syndrome, Alzheimer's disease, cerebral palsy, vertigo, amnesia and epilepsy."
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