T. Sirirutamaprapan, C. Chamtrachamnong, S. Charoenthamaha, P. Sirivongs, N. Orprasert, and B. Ngamsirimas, “A Randomized Comparison of Oral Sodium phosphate within 30 and 75 Minutes In Bowel Preparation for Colonoscopy”, Vajira Med J, vol. 50, no. 1, pp. 1–8, Sep. 2011.