1. C. Andreasen, H. Haas, and J.C. Streibig(1989 ) Floraarndringer, Forlobig status. (Preliminary report on changes in the weed flora) . 6th Danish Plant Protection Conference. Side-Effect of Pesticides/Weeds, pp.125 -133 . Statens Planteavlsforsog, Flakkebjerg, Denmark.
2. Anonymous(1985 ) SAS User Guide: Statistics , 5th edn. Institut Inc., Gary, North Carolina, 956 pp.
3. D.J. Finney(1971 ) Probit Analysis , 3rd edn , pp.66 -88 . Cambridge University Press, Cambridge.