“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.