@article {1337,
	title = {Natural abundance of 15N in forests across a nitrogen deposition gradient},
	volume = {101},
	year = {1998},
	pages = {9{\textendash}18},
	author = {Emmett, B.A. and Kj{\o}naas, O.J. and Gundersen, P. and Koopmans, C.J. and Tietema, A. and Sleep, D.}
}
