Yuliasmara, F. “El Nino Effect on Coffee Growth and Productivity on Several Agroforestry Systems in Gumitir Mountain Coffee Farms, East Java, Indonesia”. Pelita Perkebunan (a Coffee and Cocoa Research Journal), Vol. 33, no. 3, Dec. 2017, pp. 168-79, doi:10.22302/iccri.jur.pelitaperkebunan.v33i3.291.