Cleemput, O. (1997). Fertilization for sustainable plant production and soil fertility: Proceedings of the 11th International World Fertilizer Congress held at Faculty of Agricultural and Applied Biological Sciences, Universiteit Gent on 7-13 September 1997 in Gent, Belgium. Braunschweig: International Scientific Centre of Fertilizers.

Cleemput, Ovan. Fertilization for Sustainable Plant Production and Soil Fertility: Proceedings of the 11th International World Fertilizer Congress Held At Faculty of Agricultural and Applied Biological Sciences, Universiteit Gent On 7-13 September 1997 in Gent, Belgium. Braunschweig: International Scientific Centre of Fertilizers, 1997.

Cleemput, Ovan. Fertilization for Sustainable Plant Production and Soil Fertility: Proceedings of the 11th International World Fertilizer Congress Held At Faculty of Agricultural and Applied Biological Sciences, Universiteit Gent On 7-13 September 1997 in Gent, Belgium. Braunschweig: International Scientific Centre of Fertilizers, 1997.