Notes: In cooperation, DSA and Norwegian Geological Survey (NGU) have developed and published a national susceptibility map for radon (<<http://geo.ngu.no/kart/radon_mobil/?lang=eng>>) based on geology and 30 000 indoor radon ground floor measurements (Watson, R.J. et al., The use of mapped geology as a predictor of radon potential in Norway. Journal of Environmental Radioactivity 166 (2017) 341-354).  