Headache service quality: the role of specialized headache centres within structured headache services, and suggested standards and criteria as centres of excellence oleh T. J. Steiner, H. Göbel, R. Jensen, C. Lampl, K. Paemeleire, M. Linde, M. Braschinsky, D. Mitsikostas, R. Gil-Gouveia, Z. Katsarava, on behalf of the European Headache Federation and Lifting The Burden: the Global Campaign against Headache