Bellé, Soeni, and Atelene Normann Kampf. “Use of Carbonized Rice Hulls As a Horticultural Amendment for an Organic Soil”. Pesquisa Agropecuaria Brasileira, vol. 29, no. 8, Aug. 1994, pp. 1265-71, doi:10.1590/S1678-3921.pab1994.v29.4173.