1. Dzhigit, O.M., Kiselev, A.V., Mikos-Avgul’, N.N., and Shcherbakova, K.D., Dokl. AN SSSR, 1950, vol. 70, no. 3, p. 441.
2. Zolotov, Yu.A. and Kuz’min, N.M., Kontsentrirovanie mikroelementov (Preconcentration of Trace Elements), Moscow: Khimiya, 1982, p. 60.
3. Leyden, D.E., Luttrell, G.H., and Patterson, T.A., Anal. Lett., 1975, vol. 8, no. 1, p. 51.
4. Leyden, D.E. and Luttrell, G.H., Anal. Chem., 1975, vol. 47, no. 9, p. 1612.
5. Lisichkin, G.V., Kudryavtsev, G.V., Ivanov, V.M., and Figurovskaya, V.N., Zh. Vsesoyuz. Khim. O-va im. D.I. Mendeleeva, 1979, vol. 24, no. 3, p. 294.