Syahrulyati, Teti, et al. “Reserve Potential Sandy Clay As a Raw Materials Cement Village Hambalang, County Citeureup District Bogor Province Jawabarat – Indonesia”. International Journal of Engineering & Technology, vol. 7, no. 3.20, Sept. 2018, pp. 398-01, https://doi.org/10.14419/ijet.v7i3.20.20580.