9Schmid RL, Sandler AN, Katz J. Use and efficacy of low-dose ketamine in the management of acute postoperative pain: a review of current techniques and outcomes. Pain 1999; 82(2): 111 -25
10Song XJ, Zhao ZQ. Interaction between substance P and excitatory amino acid receptors in modulation of nociceptive responses of cat spinal dorsal horn neurons. Neurosci Lett 1994; 168(1 -2): 49-52
