1. Institut für Stochastik; TU Bergakademie Freiberg; D-09596 Freiberg Germany
2. Department of Forest Resource Management, Faculty of Forest Sciences; Swedish University of Agricultural Sciences (SLU); Skogsmarksgränd SE-90183 Umeå Sweden
3. German Cancer Research Center (DKFZ); Department of Biostatistics; Im Neuenheimer Feld 280 D-69120 Heidelberg Germany