Knöfel, Dietbert. “Influence of Alkalis on the Properties of Cement and Portland Cement Clinker”. Materiales de Construcción 22, no. 146 (June 30, 1972): 41–47. Accessed April 27, 2024. https://materconstrucc.revistas.csic.es/index.php/materconstrucc/article/view/1427.