Abdoullah Namdar and  Fadzil Mat Yahaya,  Oil Palm Shell Ash - Cement Mortar Mixture and Modification of Mechanical Properties.   journal   = {International Journal of Civil and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2014, vol. 86(2). 173 - 175
    [viewed 17 May 2021]. Available from: https://publications.waset.org/pdf/9997481.