1. J. A. Duke,Econ. Botany 24, 344 (1970).
2. J. R. Velasco and J. Philip,Coconut Stud. 4, 1 (1979).
3. Xike Tang and Guofeng Li,J. Chinese Rare Earth Soc. 1, 56 (1983).
4. Wei de Zhang and Xiao yun Zhang,Proceedings of Beijing conference and exhibition on instrumental analysis, (BCEIA), Vol. 1, November 18–21, 1985, pp. 821–825.
5. Huang tang Ren et al.,Biol. Trace Element Res. 7, 95 (1985).