1. Alexander, E. B., W. E. Wildman & W. C. Lynn. 1985. Ultramafic (Serpentinitic) mineralogy class. In: Kittrick, J. A., et al. (eds.), Mineral Classification of Soils, Soil Sci. Soc. Amer., Madison, WI.
2. Antonovics, J., A. D. Bradshaw & R. G. Turner. 1971. Heavy metal tolerance in plants. In: Advances in Ecological Re-search 7: 1–85.
3. Baldwin, E. M. 1959. Geology of Oregon. University of Ore-gon Cooperative Bookstore, Eugene, Oregon.
4. Barbour, M. G. and J. Major. 1977. Terrestrial Vegetation of California. John Wiley and Sons, New York.
5. Bradshaw, A. D. 1976. Pollution and evolution. In: Mansfield, T. A. (ed.), Effects of Air Pollutants on Plants, pp. 135–159. Cambridge Univ. Press.