1. Purves, D., Contamination of urban garden soils with copper and boron. Nature (Lond.)210, 1077–1078 (1966).
2. Feldman, C., Direct spectrochemical analysis of solutions. Anal. Chem.21, 1041–1043 (1949).
3. Scott, R. V., The application of direct-reading spectrochemical methods of soil analysis. Trans. Intern. Congr. Soil Sci., Madison, Wisc. U.S.A.11, (1960).
4. Mitchell, R. L., The spectrochemical analysis of soils, plants and related materials. Technical Communication No. 44A, Commonwealth Bureau of Soil Science (1964).
5. Cannon, H. L. and Bowles, J. M., Contamination of vegetation by tetra-ethyl lead. Science137, 765–766 (1962).