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	title = { Distribution and decline of endangered herbaceous heathland species in relation to the chemical composition of the soil},
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	year = {1993},
	pages = {137-143},
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}
@article {1339,
	title = {The effects of air-borne ammonium sulphate on Pinus nigra in the Netherlands},
	volume = {42},
	year = {1985},
	pages = {372{\textendash}377},
	author = {Roelofs, J.G.M. and Kempers, A.J. and Houdijk, A.L.F.M. and Jansen, J.}
}
