1. Series No. 178;Adams J.F.,1994
2. Maynard , D.N. and
Hochmuth , G.J. 1997. Knott's Handbook for Vegetable Growers,, 4th Ed. 136 ppCanada: John Wiley & Sons, Inc.
3. Tisdale , S.L.
Nelson , W.L.
Beaton , J.D. and
Havlin , J.L. 1993. Soil Fertility and Fertilizers,, 5th Ed. 379 ppNew York, NY: MacMillan Publishing Co.