1. Abundances of uranium, thorium and potassium;Clark,1966
2. Esenwein A. (1976) Private communication.
3. 1972 values for international geochemical reference samples;Flanagan;Geochim. cosmochim. Acta,1973
4. Determination of suspended and dissolved uranium in water;Fleischer;Analyt. Chem.,1976
5. The spectrophotometric determination of uranium;Florence,1970