1. Adams, W. J. 1971. U.S. Pat. No. 3,561,159 (9 Feb).
2. Improvement of Sugarbeet Seed Emergence with Dilute Acid and Growth Regulator Treatments
3. Anderson, T. P., and McGuffog, D. R. 1983. Proc. Int. Symp. Contr. Rel. Bioactive Materials, San Francisco pp. 116–124.
4. Predicting the Most Efficient Phosphorus Placement for Corn