Mattos, L. C. de, J. R. Cintra, F. E. Sanches, R. de C. M. A. da Silva, M. A. Ruiz, and H. W. Moreira. “ABO, Lewis, Secretor and Non-Secretor Phenotypes in Patients Infected or Uninfected by the Helicobacter Pylori Bacillus”. São Paulo Medical Journal, vol. 120, no. 2, Mar. 2002, pp. 55-58, https://periodicosapm.emnuvens.com.br/spmj/article/view/2677.