7Locke GR 3rd, Talley NJ, Fett SL, Zinsmeister AR, Melton LJ 3rd. Prevalence and clinical spectrum of gastroesophageal reflux: a populationbased study in Olmsted County, Minnesota. Gastroenterology, 1997, 112: 1448~1456.
8Clouse RE, Richter JE, Heading RC, Janssens J,Wilson JA. Functional esophageal disorders. Gut,1999, 45 Suppl 2: Ⅱ31~Ⅱ36.