Ferretti, M., Calderisi, M., Marchetto, A., Waldner, P., Thimonier, A., Jonard, M., Cools, N., Rautio, P., Clarke, N., Hansen, K., Merilä, P., & Potocié, N. (2015). Variables related to nitrogen deposition improve defoliation models for European forests. Annals of Forest Research, 72, 897-906. https://doi.org/10.1007/s13595-014-0445-6 (Original work published 2014)