H. Ismail, Alhassan, and Basim Sh. Abed. “Using Polyurethane Coating of Concrete Pipes With Acid Attack Resistance in Sewer Lines”. International Journal of Engineering & Technology, vol. 7, no. 4.20, Nov. 2018, pp. 118-22, https://doi.org/10.14419/ijet.v7i4.20.25861.