@article {2040,
	title = {Mapping Critical Levels for Vegetation: Chapter 3},
	year = {2017},
	month = {10/2017},
	abstract = {<p>This fully revised version of Chapter 3 of the ICP Vegetaition report includes updates to the critical levels for ozone agreed at the 30th ICP Vegetation Task Force Meeting, 14-17 February, 2017, Poznan, Poland. The critical levels for SO2, NOX and NH3 and associated text have not been changed since the previous version. This version was published in April 2017 (minor edits October 2017).</p>},
	url = {https://icpvegetation.ceh.ac.uk/publications/documents/FinalnewChapter3v4Oct2017_000.pdf},
	author = {Defra}
}
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	title = {RoTAP: Review of Transboundary Air Pollution: Acidification, Eutrophication, Ground Level Ozone and Heavy Metals in the UK},
	year = {2012},
	institution = {Centre for Ecology \& Hydrology},
	url = {http://www.rotap.ceh.ac.uk/documents},
	author = {Defra}
}
@article {317,
	title = {The Air Quality Strategy for England, Scotland, Wales and Northern Ireland (Volume 1)},
	year = {2007},
	publisher = {Department for Environment, Food \& Rural Affairs},
	url = {http://www.official-documents.gov.uk/document/cm71/7169/7169_i.pdf},
	author = {Defra}
}
@article {1551,
	title = {An introductory guide to valuing ecosystem services. },
	year = {2007},
	institution = {Defra},
	address = {London},
	url = {http://www.defra.gov.uk/wildlife-countryside/natres/eco-value.htm},
	author = {Defra}
}
