1. National Center for Health Statistics. Health, United States, 2006, with special feature on pain. Accessed December 22, 2020. https://www.cdc.gov/nchs/data/hus/hus06.pdf
2. Survey of chronic pain in Europe: Prevalence, impact on daily life, and treatment
3. Pain in primary care: an Italian survey
4. Pain as a reason to visit the doctor: a study in Finnish primary health care
5. Yakhno NN, Kukushkin ML, Churyukanov MV, Syrovegin AV. The results of the open multicenter study «MERIDIAN» to assess the prevalence of pain syndromes in outpatient practice and therapeutic preferences of physicians. Russian Journal of Pain. 2012;3-4(36-37):10-14. (In Russ.)