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2. E. STEINNES, Report KR-154. Institutt for atomenergi, Kjeller, Norway, 1977.
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4. Å. RÜHLING, L. SKÄRBY, personal communication.
5. C. BLOCK, R. DAMS, J. HOSTE, Measurement, Detection and Control of Environmental Pollutants, I.A.E.A., Vienna, 1976, p. 101.