1. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW (1988) Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip and kenn. J Rheumatol 15:1833–1840
2. Bellamy N, Kirwan J, Boers M, Prooks P, Strand V, Tugwell P, Altman R, Brandt K, Dougados M, Lequesne M (1997) Recommendations for a core set of outcome measures for future phase III clinical trials in knee, hip, and hand osteoarthritis. Consensus development at OMERACT III. J Rheumatology 24:799–802
3. Chrubasik S, Zimpfer Ch, Schütt U, Ziegler R (1996) Effectiveness of Harpagophytum procumbens in treatment of acute low back pain. Phytomedicine 3:1–10
4. Chrubasik S, Junck H, Breitschwerdt H, Conradt C, Zappe H (1999) Effectiveness of Harpagophytum extract WS 1531 in the treatment of exacerbation of low back pain: a randomized, placebo-controlled, double-blind study. Eur J Anaesthesiol 16:118–129
5. Chrubasik S, Eisenberg E, Balan E, Weinberger T, Luzzati R, Conradt C (2000) Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study. Am J Med 109:9–14