@ARTICLE {RISASI:1997, title = {Effect of root size on root nutrient concentrations of four woody trees and maize}, author = {Risasi, E. L. and Tian, G. and Opuwaribo, E. E. and Kang, B. }, journal = {Forest, Farm and Community Tree Research Report}, year = {1997}, volume = {2}, pages = {13--17}, }