1. Arnon, D. I. and Stout, P. R., Molybdenum as an essential element for higher plants. Plant Physiol.14, 599 (1939).
2. Burriel-Marti, F. and Caldas, E. F., Phenomena of coprecipitation in analysis. I. Coprecipitation of vanadium with iron, chromium and aluminium hydroxides. Anal. real. Soc. Csp. Fis. Quim.,46 B 37. Courtecy British Abstracts C. 318 (1950).
3. Feigl, F., Selective sensitive and specific reactions. Academic Press. Transl. by R. E. Oespur. New York (1949).
4. Gerretsen, F. C., On the use ofAspergillus niger for the determination of plant nutrients in the soil. Anal. Chim. Acta.2, 781 (1948).
5. Hewitt, E. J., A technique for large scale pot sand cultures. Ann. Rep. Long Ashton Res. Sta. for 1946, 37 (1947).