1. Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
2. Division of Gastroenterology and Hepatology, Department of Medicine, National University Hospital, Singapore
3. Digestive Diseases Research Institute, Wonkwang University, Iksan, Jeollabuk-do, Korea
4. Good Breath Clinic, Gunpo, Gyeonggi-do, Korea