Achalasia Previously Diagnosed as Gastroesophageal Reflux Disease by Relying on Esophageal Impedance-pH Monitoring: Use of High-Resolution Esophageal Manometry in Children. - Jung Eun Pyun; Da Min Choi; Jung Hwa Lee; Kee Hwan Yoo; Jung Ok Shim (Pediatric Gastroenterology, Hepatology & Nutrition, 2015)