Morlion, B., Walch, H., Yihune, G., Vielvoye-kerkmeer, A., et al. (2008). The Pain Associates' International Network initiative: A novel practical approach to the challenge of chronic pain management in Europe. Pain Practice, 8(6), 473 - 480.

Beubler, E., Eisenberg, E., Castro-Lopes, J., & Rhodin, A. (2007). Prescribing policies of opioids for chronic pain. Journal of Pain and Palliative Care Pharmacotherapy, 21(2), 53 - 55.