Van Miegroet, Helga, Dale W. Johnson, and Donald E. Todd. "Foliar Response of Red Spruce                        Saplings to Fertilization with Ca and Mg in the Great Smoky Mountains                        National Park." Canadian Journal of Forest                        Research 23, no. 1 (1993): 89-95.

Johnson, Dale W., Helga Van Miegroet, Steven E. Lindberg, Donald E. Todd, and Robert B. Harrison. "Nutrient Cycling in Red Spruce Forests of the Great Smoky Mountains." Canadian Journal of Forest Research 21, no. 6 (1991): 769-787.

Van Miegroet, Helga, Dale W. Johnson, Donald E. Todd, and J. D. Goodlaxson. Nitrogen Dynamics in High-Elevation Spruce Sites in the Great Smoky Mountains National Park In First Annual Southern Appalachian Man and the Biosphere Conference. Gatlinburg, TN: Tennessee Valley Authority, 1990.