Relaxation Therapy for patients suffering from chronic pain

Hi
I`m a student from Esbjerg physiotherapy school in Denmark and at the moment me and my group are in the proces of writing a bachelor project about relaxation therapy for patients with chronic pain. The focus of the project is going to be whether the treatment has got any effect or not and if yes, then which kind of effect. We want to investigate both the physiological as well as the psycological effects.
Therefore we are looking for people with experience in this field. Maybe someone can suggest good litterature or scientific work on this subject?
We would be very happy for all the help we can get!

sincerely Nanna Krukow