J. Zool., 61: 505-511 (1983). Roshon, R.D., "Genecological Studies on Two Populations of Betula pumila var. giandulifera, with Special Reference to Their Ecology and Metal Tolerance", M. Sc.
Rossmann, R. et J. Barnes, «Trace Element Concentrations in Near-surface Waters of the Great Lakes, and Methods of Collection, Storage and Analysis», J. Great Lakes Res., 14: 188-204 (1988).