Atman, Atman, et al. “Effect of Cow Manure Dosages as Organic Fertilizer on the Productivity of Organic Rice in West Sumatra, Indonesia.” International Journal of Environment, Agriculture and Biotechnology, vol. 3, no. 2, 2018, pp. 506–11. Crossref, https://doi.org/10.22161/ijeab/3.2.25.