Prospective, randomized, controlled comparison of the use of polyethylene glycol electrolyte lavage solution in four-liter versus two-liter volumes and pretreatment with either magnesium citrate or bisacodyl for colonoscopy preparation. - Sharma,V.K.; Chockalingham,S.K.; Ugheoke,E.A. (Gastrointest Endosc, 1998)