Van Den Berg LJL, Vergeer P, Rich TCG, Smart SM, Guest D, Ashmore MR. Direct and indirect effects of nitrogen deposition on species composition change in calcareous grasslands. Global Change Biology. 2010  ;17:1871-83.

Smart SM, Ashmore MR, Hornung M. Detecting the signal of atmospheric N  deposition in recent national-scale vegetation change across Britain. Water, Air and  Soil Pollution: Focus. 2004  ;4:269?278.