Variability in concentrations of potentially toxic elements in urban parks from six European cities

L. Madrid, Encarnation Diaz-Barrientos, E. Ruiz-Cortes, R. Reinoso, M. Biasioli, Christine Davidson, A.C. Duarte, H. Grcman, I. Hossack, A S Hursthouse, T. Kralj, K. Ljung, E. Otabbong, S. Rodrigues, Graham John Urquhart, F. Ajmone-Marsanb