3Deibert E J, Utter R A. Earthworm ( Lumbricidae ) survey of North Dakota fields placed in the U. S. Conservation Reserve Program. Soil and Water Conservation, 2003, 58 (1) : 39 -45.
4Oliveira R S, Vnsatka M, Dodd J C, et al. Studies on the diversity of arbuscular mycorrhizal fungi and the efficacy of two native isolates in a high- ly alkaline anthropogenic sediment. Mycorrhiza, 2005, 16 ( 1 ) .. 1 - 9.
5Hatch D J, Lovell R D, Antil R S, et al. Nitrogen mineralizstion and microbial activity in permanent pastures amended with nitrogen fertilizer or dung. Biol. Fertil. Soils, 2000, (30): 288 -293.