Perera และผู้แต่งคนอื่นๆ. 2007. Utilization of sludge from biyagama common wastewater treatment plant as fertilizer and soil conditioner in Sri Lanka. Field of Study Industrial Ecology and Environment, Mahidol University;
Perera และผู้แต่งคนอื่นๆ. (2007) Utilization of sludge from biyagama common wastewater treatment plant as fertilizer and soil conditioner in Sri Lanka . Mahidol University/Bangkok.
Perera และผู้แต่งคนอื่นๆ. Utilization of sludge from biyagama common wastewater treatment plant as fertilizer and soil conditioner in Sri Lanka. . Bangkok:Mahidol University, 2007.
Perera และผู้แต่งคนอื่นๆ. (2007) Utilization of sludge from biyagama common wastewater treatment plant as fertilizer and soil conditioner in Sri Lanka . Mahidol University/Bangkok.