Disorders of the Nervous System Caused by Drugs, Toxins, and Chemical Agents, Opiates and Synthetic Analgesic Drugs
Adams & Victors Principles of Neurology Chp 43, pg 1201, Ropper, A.H.,et al, 2014
Treatment of Herpes Zoster and Postherpetic Neuralgia
BMJ 326:748-750, Johnson,R.W. &Dworkin,R.H., 2003