Raatikainen, Timo, et al. “Effect of Glycosaminoglycan Polysulfate on Chondromalacia Patellae: A Placebo-Controlled 1-Year Study”. Acta Orthopaedica, vol. 61, no. 5, Jan. 1990, pp. 443-8, doi:10.3109/17453679008993559.