Kalyan Kr. Mandal and  Suresh Thokchom and  Mithun Roy,  Effect of Na2O Content on Performance of Fly ash Geopolymers at Elevated Temperature.   journal   = {International Journal of Geological and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2011, vol. 49(1). 7 - 13
    [viewed 21 January 2020]. Available from: https://publications.waset.org/pdf/3294.