Rum, Rahmat Hidayat Mohammed, et al. “Density and Strength of Foamed Concrete: The Influence on Dynamic Characteristics of Lightweight Profiled Composite Slabs”. International Journal of Integrated Engineering, vol. 11, no. 6, Sept. 2019, pp. 285-9, https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/4952.