SEMBIRING, Mariani, et al. “Effect of Soil Conditioner Enriched With Biofertilizers to Improve Soil Fertility and Maize (Zea Mays L.) Growth on Andisols Sinabung Area”. Acta Agriculturae Slovenica, vol. 116, no. 2, Dec. 2020, pp. 253–260, https://doi.org/10.14720/aas.2020.116.2.1322.