References:

Van Tulder, M., Becker, A., Bekkering, T., Breen, A., del Real, M.T., Hutchinson, A., Koes, B., Lærum, E., Malmivara, A. (2006).
Chapter 3. European Guidelines for the Management of Acute Nonspecific Low Back Pain in Primary Care
European Spine Journal 2006 (Mar); 15 Suppl 2: S169–191