Martin, MD, G., M. Hartmannsgruber, MD, E. Riley, MD, and G. Manvelian, MD. “Single-Dose Extended-Release Epidural Morphine for Pain After Hip Arthroplasty”. Journal of Opioid Management, vol. 2, no. 4, July 2006, pp. 209-18, doi:10.5055/jom.2006.0033.