@article {283, title = {Human impacts on the nitrogen cycle: A global problem judged from a local perspective}, journal = {Ambio}, volume = {26}, year = {1997}, pages = {321-325}, author = {Hessen, D.O. and Henriksen, A. and Hindar, A. and Mulder, J. and Torseth, K. and Vagstad, N.} }