1. Official Methods of Analysis;Association of Official Analytical Chemists,1970
2. Official Methods of Analysis;Association of Official Analytical Chemists,2006
3. Organic matter, soil properties, and wheat production in the high valley of Mexico;Bell;Soil Sci.,1993
4. Quality in Anthurium andreanum and Aechmea fasciata grown in peat substrates as affected by nitrogen and potassium nutrition;Bik;Acta Hortic.,1976
5. Ecological aspects of plant mineral nutrition;Chapin,1988