Schmucki, R., Pe’er, G., Roy, D.B., Stefanescu, C., Van Swaay, C.A., Oliver, T.H., Kuussaari, M., Van Strien, A.J., Ries, L., Settele, J., Musche, M., Carnicer, J., Schweiger, O., Brereton, T.M., Harpke, A., Heliölä, J., Kühn, E. & Julliard, R. (2016) A regionally informed abundance index for supporting integrative analyses across butterfly monitoring schemes. Journal of Applied Ecology, 53, 501–510.