1. Nitrogen saturation in northern forest ecosystems: Hypothesis and implications;Aber;BioScience,1989
2. Towards a National Acid Rain Strategy,1997
3. Emission and deposition of ammonia and ammonium;Asman;Nova Act Leopoldina NF 70,1994
4. Ammonia emission in Europe: updated emission and emission variations;Asman,1992
5. Farm Inputs Management Survey, 1995;Agriculture and Agri-Food Canada and Statistics Canada,1996