Dutch Butterfly Conservation produced an analysis in 2004 for the ETCNPB. This analysis was subcontracted and resulted to results and figures. These results and figures are free of copyrights for publications (edition, web, ...). Dutch Butterfly Conservation should be cited in any of these publications.
The bird trends reflect the period 1980-2002. The butterfly trends reflect the period 1972/73-1997/98. The names of the bird species taken into account are listed in the methodology for calculating the core set indicator on Species Diversity (CSI009).