主题：【已应助】求助4篇文献，还剩2

【篇号】1
【作者】Damodar Reddy, D., Subba Rao, A. and Takkar, P. N.
【文章标题】Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation.
【期刊名，年份，卷（期），起止页码】Biology and Fertility of Soils 1999. 28(2):150-155.       
【全文链接】http://link.springer.com/article/10.1007/s003740050477#
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【篇号】2
【作者】McKeague, J. A., Brydon, J. E. and Miles, N. M.
【文章标题】 Differentiation of forms of extractable iron and aluminum in soils1.
【期刊名，年份，卷（期），起止页码】Soil Science Society of America Journal 1971. 35(1):33-38.       
【全文链接】https://dl.sciencesocieties.org/publications/sssaj/abstracts/35/1/SS0350010033
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【篇号】3
【作者】Pastor, J., Aber, J. D., McClaugherty, C. A. and Melillo, J. M.
【文章标题】Above-ground production and n and p cycling along a nitrogen mineralization gradient on blackhawk island, wisconsin.
【期刊名，年份，卷（期），起止页码】Ecology 1984. 65(1):256-268.
【全文链接】http://www.esajournals.org/doi/abs/10.2307/1939478
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【篇号】4
【作者】Scheffer, M.
【文章标题】Multiplicity of stable states in freshwater systems.
【期刊名，年份，卷（期），起止页码】Hydrobiologia 1990. 200:475-486.
【全文链接】http://link.springer.com/chapter/10.1007/978-94-017-0924-8_42
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