WHO Handbook on Indoor Radon: a public health perspective
Gray, A. (2009). Cost Effectiveness of Radon Control. In: World Health Organisatio Handbook On Indoor Radon, a Public Health Perspective. Ed by Hajo Zeeb and Ferid Shannoun.
The handbook is available to download here
Further details and an online version are available from the WHO website at: http://www.who.int/phe/en/