Gertner, G., & Köhl, M. (1995). An example of some problems with nonsampling errors in nontimber surveys. In M. Köhl, P. Bachmann, P. Brassel, & G. Preto (Eds.), The Monte Verità Conference on Forest Survey Designs. «Simplicity versus Efficiency» and Assessment of Non-Timber Resources (pp. 177-190). Swiss Federal Institute for Forest, Snow and Landscape Research (WSL/FNP); Swiss Federal Institute of Technology (ETH).