1. EC, Enhanced radioactivity of building materials. Radiation protection 96, European Commission, Luxembourg, 1999a.
2. EC, Council directive 2013/59/EURATOM of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionizing radiation, Off. J. Eur. Union, L 13/1, 2013.
3. EC, Radiological protection principles concerning the natural radioactivity of building materials. Radiation protection 112, European Commission, Luxembourg, 1999b.
4. NEN, Radioactivity measurements – Determination of the natural radioactivity in stony building materials by means of semiconductor gamma ray spectrometry. NEN 5697(en). Nederlands Normalisatie-instituut, Delft, The Netherlands, 2001.
5. SI, Content of Natural Radioactive Elements in Building Products, Standard of Israel No. 5098, Standards Institute of Israel, Tel-Aviv, Israel, 2010.