Citation
Gregory, R.D., van Strien, A., Vorisek, P., Meyling, A.W.G., Noble, D.G., Foppen, R.P.B. & Gibbons, D.W. 2005. Developing indicators for European birds. Philosophical Transactions of the Royal Society B 360: 288. doi:10.1098/rstb.2004.1602
