Evizal, R., T. Tohari, I. D. Prijambada, J. Widada, and D. Widianto. “Ecosystem Service of Shade Trees on Nutrient Cycling and Productivity of Coffee Agro-Ecosystems”. Pelita Perkebunan (a Coffee and Cocoa Research Journal), Vol. 25, no. 1, May 2009, doi:10.22302/iccri.jur.pelitaperkebunan.v25i1.108.