এই পাঠটি: Soil fertility and fertilizers : an introduction to nutrient management / John L. Havlin, North Carolina State University, Samuel L. Tisdale, late President, the Sulphur Institute, Werner L. Nelson, late Senior Vice President, Potash & Phosphate Institute, James D. Beaton, retired from Potash & Phosphate Institute and Potash & Phosphate Institute of Canada, formerly at Cominco Ltd., the Sulphor Institute, Ag Canada, and University of British Columbia.