Kogel, G. “Faced Concrete Block. New Developments May Be Concrete masonry´s Answer to Competitive Challenge”. Materiales de Construcción 7, no. 078 (February 28, 1957): 45–46. Accessed February 24, 2025. https://materconstrucc.revistas.csic.es/index.php/materconstrucc/article/view/2062.