A Randomized, Double-Blind, Crossover Comparison of the Efficacy and Safety of Oral Controlled-Release Tramadol and Placebo in Patients with Painful Osteoarthritis oleh Carter Thorne, André D Beaulieu, Denis J Callaghan, William F O’Mahony, John M Bartlett, Richard Knight, Gunnar R Kraag, Ronald Akhras, Paula S Piraino, John Eisenhoffer, Zoltan Harsanyi, Andrew C Darke