N. Boontian,  Conditions of the Anaerobic Digestion of Biomass.   journal   = {International Journal of Environmental and Ecological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2014, vol. 93(9). 1036 - 1040
    [viewed 15 September 2019]. Available from: https://publications.waset.org/pdf/9999472.