Lumbantobing, H. et al. 2011. The Profile of Upper Gastrointestinal Endoscopy in Deli Serdang Hospital. The Indonesian Journal of Gastroenterology, Hepatology, and Digestive Endoscopy. 12, 1 (Jan. 2011), 34–37. DOI:https://doi.org/10.24871/121201134-37.