1. Total colonoscopy: is it always possible?;Waye;Gastrointest Endosc,1991
2. Colonoscopy: How difficult? How painful?;Hull;Dis Colon Rectum,1994
3. How difficult is colonoscopy?;Nivatvongs;Gastrointest Endosc,1982
4. The association between gender and difficult colonoscopy;Schmitt;Gastrointest Endosc,1994
5. Does prior abdominal or pelvic surgery affect length of insertion of the colonoscope?;Ravi;Endoscopy,1988