Rudžionis, Žymantas, and Ernestas Ivanauskas. “Investigations into Effective Fly Ash Used in Concrete”. Journal of Civil Engineering and Management 10, no. 4 (December 31, 2004): 303-309. Accessed April 2, 2020. https://journals.vgtu.lt/index.php/JCEM/article/view/9000.