Nitrogen Surplus—A Unified Indicator for Water Pollution in Europe? oleh Susanne Klages, Claudia Heidecke, Bernhard Osterburg, John Bailey, Irina Calciu, Clare Casey, Tommy Dalgaard, Hanna Frick, Matjaž Glavan, Karoline D’Haene, Georges Hofman, Inês Amorim Leitão, Nicolas Surdyk, Koos Verloop, Gerard Velthof