1. Spatial variability of nitrogen in soils;Biggar,1978
2. El maíz y su sistema de manejo;Bratos;Fertilización,1990
3. Characterization of the kinetics of coated nitrogenous fertilizers desorption and its relationship with leaching and absorption;Cartagena;Fert. Res.,1991
4. Revisión del método de determinación automatizada del Nitrógeno U.V oxidable en extractos de suelo;Díez;Anal. Edafol. Agrobiol.,1988
5. Council directive on the quality of water for human consumption;European Economic Community;Official Journal 23, No. 80/778 EEC L229,1980