Health Symptoms A to Z (2)

Healthline Media, San Francisco, USA

Resource Library (2)

Society of Teachers of Family Medicine, Leawood , USA

Society of Teachers of Family Medicine (2)

Society of Teachers of Family Medicine, Leawood, KS, USA

International Textbook of Obesity (2)

Book, John Wiley & Sons, Inc., Hoboken, USA, free summaries, paid full-text chapters

Internet Drug Index (2)

RxList Inc., New York, USA

Lab Tests Online (2)

Lab Test Online, American Association for Clinical Chemistry, Washington, USA

Mayo Clinic Medical Laboratories (2)

Mayo Clinic, Rochester, MN, USA

ECG Library (4)

Edward Burns

Medical Information (2)

MedicineNet, Inc., WebMD LLC, New York, USA

Medicína po promoci (2)

Journal, MEDICAL TRIBUNE CZ, s.r.o., Prague, Czech Republic, in Czech

National Council on Aging (2)

National Council on Aging, Arlington, USA

National Institute on Ageing (2)

National Institute on Ageing, National Institutes of Health, Bethesda, USA