Unlugenc, MD, H., Gunduz, MD, M., Guzel, MD, B. and Isik, MD, G. (2012) “A comparative study on the effects of intrathecal morphine added to levobupivacaine for spinal anesthesia”, Journal of Opioid Management, 8(2), pp. 105–113. doi: 10.5055/jom.2012.0103.