George, MD, J. A., Lin, MD, E. E., Hanna, MD, M. N., Murphy, MD, J. D., Kumar, MD, K., Ko, BS, P. S. and Wu, MD, C. L. (2018) “The effect of intravenous opioid patient-controlled analgesia with and without background infusion on respiratory depression: A meta-analysis”, Journal of Opioid Management, 6(1), pp. 47–54. doi: 10.5055/jom.2010.0004.