M. S. Walid, MD, PhD, L. Hyer, PhD, M. Ajjan, MD, A. C. M. Barth, and J. S. Robinson, Jr, MD, “Prevalence of opioid dependence in spine surgery patients and correlation with length of stay”, J of Opioid Management, vol. 3, no. 3, pp. 127–132, May 2007.