Burden and attitude to resistant and refractory migraine: a survey from the European Headache Federation with the endorsement of the European Migraine & Headache Alliance oleh Simona Sacco, Christian Lampl, Antoinette Maassen van den Brink, Valeria Caponnetto, Mark Braschinsky, Anne Ducros, Patrick Little, Patricia Pozo-Rosich, Uwe Reuter, Elena Ruiz de la Torre, Margarita Sanchez Del Rio, Alexandra J. Sinclair, Paolo Martelletti, Zaza Katsarava, On behalf of the Burden and Attitude to Resistant and Refractory (BARR) Study Group