Ramlan Zailani and  Halim Ghafar and  Mohamad Sofian So'aib,  Effect of Oxygen on Biochar Yield and Properties.   journal   = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2013, vol. 73(1). 119 - 123
    [viewed 11 December 2019]. Available from: https://publications.waset.org/pdf/10316.