Pirone, P.P., Hartman, J.R., Sall, M.A. and Pirone, T. P., "Tree Maintenance", Oxford University Press, NY 1988.
Sinclair, Wayne A., Lyon, Howard H. and Johnson, Warren T., "Diseases of Trees and Shrubs", Cornell University Press, Ithaca NY, 1987.
University of Minnesota Extension, "Pruning Trees and Shrubs", FO-00628, Mike Zins and Deborah Brown, 2002; www.extension.umn.edu/distribution/horticulture/DG0628.html
University of Minnesota Extension, "A Practitioner's Guide to Stem Girdling Roots", BU-07501, Gary R. Johnson and Richard J. Hauer, 2002; http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/practitioners-guide-to-stem-girdling-roots/.html
University of Minnesota Extension "Tree Fertilization: A Guide for Fertilizing New and Established Trees in the Landscape", FO-07410, Jeff Gillman and Carl Rosen, 2000; http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/tree-fertilization-guide/
University of Minnesota Extension "Protecting Trees and Shrubs Against Winter Damage", FO-01411, Bert T. Swanson and Richard Rideott, 2004; http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-from-winter-damage/
University of Wisconsin Extension, "Caring for Your Established Shade Trees", A1817, E.R. Hasselkus, 1993; https://learningstore.uwex.edu/Assets/pdfs/A1817.pdf
University of Wisconsin Extension, "Caring for Deciduous Shrubs", A1771, E.R. Hasselkus, 1999; https://learningstore.uwex.edu/Assets/pdfs/A1771.pdf
University of Wisconsin Extension, "Deciduous Shrubs, How to Properly Prune", X1015, Laura Jull, 1999; http://www.uwex.edu/ces/wihort/gardenfacts/X1015.pdf
University of Wisconsin Extension, "Deciduous Trees, How to Properly Prune", X1014, Laura Jull, 1999; www.uwex.edu/ces/wihort/landscape/Publications.htm
University of Wisconsin Extension, "Evergreens - Planting and Care", A1730, E.R. Hasselkus, http://learningstore.uwex.edu/Assets/pdfs/A1730.pdf