%0 Report %D 1996 %T Empirical nitrogen critical loads for natural and semi-natural ecosystems %A Bobbink, R. %A Hornung, M. %A Roelofs, J.G.M. %B in B. Werner and T. Spranger, editors. Manual on methodologies and criteria for mapping critical loads/levels. UN ECE Convention on Long-range Transboundary Air Pollution. %I Umweltbundesamt %C Berlin %P 71-96. %G eng