1. Instituto Aliaga; Barcelona Spain
2. Millennium Pain Center; Bloomington Illinois U.S.A.
3. Illinois Wesleyan University; Bloomington Illinois U.S.A.
4. Department of Anesthesiology; Pain Clinic; Hospital Universitari de Bellvitge; Barcelona Spain
5. Pain Unit; Department of Anesthesiology; Hospital Clínic de Barcelona; Universitat de Barcelona; Barcelona Spain