6Reinink K, Nes M V, Groenwold R, et al. Genetic variation for nitrate content between cultivars of endive ( Cichorium endivia L). Euphytica. 1994, 75:41-48.
7Reinink K, Eenink A H. Genotypical differences in nitrate accumulation in shoots and roots of lettuce. Scientia Horticulturae, 1988, (37) : 13- 24.
8Satarug S, Baker J R, Urbenjapol S, et al. A global perspective on cadmium pollution and toxicity in non-occupationally exposed poptdation. Tcoticology Letters, 2003, 137 (1, 2): 65-83.
9Ebbs S D, Lasat M M, Brady D J, etal. Phytoextration of cadmiurm and Zinc form a contaminated soil. J. Environ. Qual., 1997, 26:1424-1430.