1. H.A.V.D. Sloot, J.B. Luten, Petten, Netherlands /1976/.
2. H.A.V.D. Sloot, ECN-1, Petten, Netherlands /1976/.
3. J. Wijkstra, H.A.V.D. Sloot, R. Massée, ECN-80-008, Petten, Netherlands /1980/.
4. M.K. Sherif, R.M. Awadallah, F. Grass,Bull. Fac. Sci., Assiut Univ., Egypt, 7 /1978/ 379.
5. M.K. Sherif, R.M. Awadallah, F. Grass,J. Radioanal. Chem., 60 /1980/ 267.