E. Santosa, A. D. Susila, A. P. Lontoh, A. Noguchi, K. Takahata, and N. Sugiyama, “NPK Fertilizers for Elephant Foot Yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) Intercropped with Coffee Trees”, J. Agron. Indonesia (Indonesian J. Agron.), vol. 43, no. 3, pp. 257–263, Feb. 2016, doi: 10.24831/jai.v43i3.11253.