2[36]Ciociola AA,Mcsorley DJ,Turner K,et al.Helicobacter pylori infection rates in duodenal ulcer patients in the United States may be lower than previously estimated.Am J Gastroenterol 1999;94:1839
3[37]Wong BC,Lam SK,Ching CK,et al.Seroprevalence of cytotoxin associated gene A positive of Helicobacter pylori strains in Change. an area with high prevalence of gastric cancer in south China.Aliment Pharmacol Ther 1999;13:1295
