Cost of healthcare for patients with migraine in five European countries: results from the International Burden of Migraine Study (IBMS) - Bloudek, LM; Stokes, M; Buse, DC; Wilcox, TK; Lipton, RB; Goadsby, PJ; Varon, SF; Blumenfeld, AM; Katsarava, Z; Pascual, J; Lanteri-Minet, M; Cortelli, P; Martelletti, P (J Headache Pain, 2012)