1. Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study 
Sigrun Chrubasik, MD, Elon Eisenberg, MD, Edith Balan, MD, Tuvia Weinberger, MD, Rachel Luzzati, MD, Christian Conradt, PhD 
The American Journal of Medicine 
Volume 109, Issue 1, Pages 9-14 (July 2000)
DOI: /S (00)

2. Figure 1
Percentage of patients who were pain free without rescue medication in weeks 1 to 4 in the placebo, and in the low-dose and high-dose willow bark groups.
The American Journal of Medicine  , 9-14DOI: ( /S (00) )