Henle, K., B. Bauch, M. Auliya, M. Külvik, G. Pe'er, D. S. Schmeller, Framstad E. (2013) Priorities for biodiversity monitoring in Europe: a review of supranational policies and a novel scheme for integrative prioritization Ecological Indicators 33: 5-18. http://www.sciencedirect.com/science/article/pii/S1470160X13001416