Réquiz, R., N. Vera, and S. Camero. “The Influence of Surface Roughness on the Hydrogen Permeation of Type API 5L-X52 Steel”. Revista De Metalurgia, vol. 40, no. 1, Feb. 2004, pp. 30-38, doi:10.3989/revmetalm.2004.v40.i1.240.