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Links

9. Stovner, L. J.; Hagen, K; Jensen, R.; Katsarava, Z.; Lipton, R. B.; Scher, A.I.; Steiner, T. J. & Zwart, J-A. "The global burden of headache: a documentation of headache prevalence and disability worldwide". Cephalalgia, Vol.27, pp.193–210. 2007.