6Stal P, Lindberg G, Ost A, Iwarzon M, Seensalu R. Gastroesop- hageal reflux in healthy subjects. Significance of endosco-pic findings, Histology, Age and Sex[J]. Scand J Gastroentrol, 1999,34: 121-128
7Schnatz PF, Castell JA, Castell DO. Pulmonary symptoms associated with gastroesophageal reflux: use of ambulatory pH monitoring to diagnose and to direct therapy[J]. Am J Gastroenterol, 1996.91 : 1715