Notes: See radon webpage on website of National Institute for Public Health and the Environment (RIVM, Rijkstinstituut voor Volksgezondheid en Milieu), <<https://www.rivm.nl/radon-en-thoron>>. See also Journal of Environmental Radioactivity 165 (2016), 93-102, <<https://doi.org/10.1016/j.jenvrad.2016.09.008>>
  