Wetzel FT, Bingham HC, Groom Q, Haase P, Kõljalg U, Kuhlmann M, Martin CS, Penev L, Robertson T, Saarenmaa H, Schmeller DS, Stoll S, Tonkin JD, Häuser CL, 2018, Unlocking biodiversity data: Prioritization and filling the gaps in biodiversity observation data in Europe, Biological Conservation, 221, 78–85, https://doi.org/10.1016/j.biocon.2017.12.024