WASET
    Hanizam Awang and  Mohammed Zuhear Al-Mulali,  Utilising Unground Oil Palm Ash in Producing Foamed Concrete and Its Implementation as an Interlocking Mortar-Less Block.   journal   = {International Journal of Civil and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    February 2016, vol. 111(3). 347 - 352
    [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/10003993.