WASET
    Olga Velts and  Mai Uibu and  Juha Kallas and  Rein Kuusik,  Prospects in Waste Oil Shale Ash Sustainable Valorization.   journal   = {International Journal of Chemical and Molecular Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2011, vol. 52(4). 331 - 335
    [viewed 19 April 2024]. Available from: https://publications.waset.org/pdf/2849.