Two Liters of Polyethylene Glycol-Electrolyte Lavage Solution Versus Sodium Phosphate as Bowel Cleansing Regimen for Colonoscopy: A Prospective Randomized Controlled Trial - Poon, C M; Lee, D W H; Mak, S K; Ko, C W; Chan, K C; Chan, K W; Sin, K S; Chan, A C W (Endoscopy, 2002)