Santosa, Edi, Anas Dinurrohman Susila, Adolf Pieter Lontoh, Arisa Noguchi, Ken Takahata, and Nobuo Sugiyama. 2016. “NPK Fertilizers for Elephant Foot Yam (Amorphophallus Paeoniifolius (Dennst.) Nicolson) Intercropped With Coffee Trees”. Jurnal Agronomi Indonesia (Indonesian Journal of Agronomy) 43 (3), 257-63. https://doi.org/10.24831/jai.v43i3.11253.