Gonzalesbatista, A., Hernandezmoreno, JM., Fernandezcaldas, E., & Herbillon, AJ. (1982). Influence of Silica Content On the Surface-charge Characteristics of Allophanic Clays. Clays and Clay Minerals, 30(2), 103-110. https://doi.org/10.1346/CCMN.1982.0300204 (Original work published 1982)