3Thomas A C.Weed survey system used in Saskatchewan for cere-al and oilseed crops[ J].Weed Science, 1985,33:34-43.
4Buhler D D,Liebaman M,Obrycki J J.Theoretical and practicalchallenges to an IPM approach to weed management[ J].WeedScience ,2000,48:274-280.
5Thomas A C. Weed survey system used in Saskatchewan for cereal and oilseed crops[ J ]. Weed Science, 1985,33:34 - 43.
6Buhler D D, Liebaman M, Obrycki J J. Theoretical and practical chal- lenges to an IPM approach to weed management[ J ]. Weed Science, 2000,48:274 -280.
7Thomas A C. Weed survey system used in Saskatchewan for ce- real and oilseed erops[J]. Weed Science, 1985, 33: 34-43.
8Thomas A C.Weed survey system used in Saskatchewan for cereal and oilseed crops[J].Weed Science,1985,33:34-43.
