Situmeang, Yohanes Parlindungan, et al. “Effect of Dose Biochar Bamboo, Compost, and Phonska on Growth of Maize (Zea Mays L.) in Dryland”. International Journal on Advanced Science, Engineering and Information Technology, vol. 5, no. 6, Dec. 2015, pp. 433-9, doi:10.18517/ijaseit.5.6.609.