Nutrient Resources for Crop Production in the Tropics: Discussion Henzell, T. ; Vlek, P. L. G. ; Wood, P. ; Leggo, P. J. ; Giller, K. ; Powlson, D. S. ; Hayes, M. H. B. ; Sanchez, P. Abstract Publication: Philosophical Transactions of the Royal Society of London Series B Pub Date: July 1997 Bibcode: 1997RSPTB.352..984H