Potts S.G., Biesmeijer J.C., R Bommarco, Felicioli A., Fischer M., Jokinen P., Kleijn D., Klein A-M, Kunin W.E., Neumann P., Penev L.D., Petanidou T., Rasmont P., Roberts S.P.M., Smith H.G., Sørensen P.B., Steffan-Dewenter I., Vaissière B.E., Vilà M., Vujić A., Woyciechowski M., Zobel M., Settele J.& Schweiger O. (2011) Developing European conservation and mitigation tools for pollination services: approaches of the STEP (Status and Trends of European Pollinators) projectJournal of Apicultural Research 50(2): 152-164. http://www.ibra.org.uk/articles/Conserving-European-Pollinators