European Commission. (1997). Radiation protection 88: Recommendations for the implentation of title VII of the european basic safety standards directive(BSS) concerning significant increase in exposure due to natural radiation sources. Luxembourg: Office for Official Publications of the European Communities.

European Commission. Radiation Protection 88: Recommendations for the Implentation of Title VII of the European Basic Safety Standards Directive(BSS) Concerning Significant Increase in Exposure Due to Natural Radiation Sources. Luxembourg: Office for Official Publications of the European Communities, 1997.

European Commission. Radiation Protection 88: Recommendations for the Implentation of Title VII of the European Basic Safety Standards Directive(BSS) Concerning Significant Increase in Exposure Due to Natural Radiation Sources. Luxembourg: Office for Official Publications of the European Communities, 1997.