J.M. Klap, P.W. Goedhart, C. van der Salm, J.H. Oude Voshaar, A. Bleeker, C.M.A. Hendriks, S.M.J. Wijdeven, A.F.M. Olsthoorn, F. de Vries, J.C.H. Voogd, W. de Vries,
Relationships between crown condition and its determining factors in the Netherlands for the period 1984 to 1994 Alterra. ,(2000)