Maslekar, S. K., Hughes, M., Skinn, E., Gardiner, A., Culbert, B., & Duthie, G. S. (2006). Randomised controlled trial of sedation for colonoscopy: Entonox versus intravenous sedation. GASTROINTESTINAL ENDOSCOPY, 63(5), AB97. https://doi.org/10.1016/j.gie.2006.03.087