Ma, Huan-Zhi, et al. “Temporal and Spatial Expression of BMP-2 in Sub-Chondral Bone of Necrotic Femoral Heads in Rabbits by Use of Extracorporeal Shock Waves”. Acta Orthopaedica, vol. 79, no. 1, Jan. 2008, pp. 98-105, doi:10.1080/17453670710014833.