Wong CA, Fragen RJ, Fitzgerald P, McCarthy RJ. A comparison of the SNAP II™ and BIS XP™ indices during sevoflurane and nitrous oxide anaesthesia at 1 and 1.5 MAC and at awakening. British Journal of Anaesthesia. 2006 Aug;97(2):181–6. doi: 10.1093/bja/ael131.