1. Hartog, F.A., Knaepen, W.A.I., Jonkers, G., 1995. Radioactive lead: An Underestimated Issue?, Proceedings of the API/GRI NORM Conference, Houston, USA, p. 59–69.
2. Tenorm in oil, gas and mineral mining;Heaton;App. Radiat. Isot.,1995
3. IAEA, 1988. Principles for the exemption of radiation and practices from regulatory control, Safety Series No.89, IAEA, Vienna.
4. IAEA, 1994. International basic safety standards for the protection against ionizing radiation and for the safety of radiation sources, GOV/2715/94, IAEA, Vienna.