Engelhardt, MD, PhD, FRCA, T., Zaarour, MD, C. and Crawford, MBBS, FRCPC, M. W. (2017) “Plasma cyclic guanosine 3′,5′-monophosphate levels: A marker of glutamate-nitric oxide-guanyl cyclase activity?”, Journal of Opioid Management, 7(6), pp. 462–466. doi: 10.5055/jom.2011.0087.