@article {159,
	title = {Empirical nitrogen critical loads: update since Lokeberg (1992)},
	year = {1995},
	pages = {9-19},
	institution = {Institute of Terrestrial Ecology},
	address = {Bush},
	author = {Bobbink, R. and Roelofs, J.G.M.},
	editor = {Hornung, M. and Sutton, M.A. and Wilson, R.B.}
}
@inbook {188,
	title = {Acid rain since 1985 - times are changing},
	booktitle = {Acid deposition: its nature and impacts},
	series = {Proceedings of the Royal Society of Edinburgh},
	volume = {97},
	year = {1991},
	pages = {1-15},
	author = {Brydges, T.G. and Wilson, R.B.},
	editor = {Last, F.T. and Watling, R.}
}
