Books:

Forest Trees of Oklahoma Manual, Oklahoma Department of Agriculture—Forestry Services, Oklahoma City, OK.

Manual of Woody Landscape Plants, Dirr, Michael A. 1998. Stipes Publishing Company: Champaign, IL.

Websites:

Basics of Tree ID—Leaf Key
http://www.fw.vt.edu/dendro/forsite/Idtree.htm

Identification of Common Trees of Iowa
http://www.exnet.iastate.edu/pages/tree

Vascular Plant Image Gallery
http://www.csdl.tamu.edu/FLORA/gallery.htm

American Forests Organization
http://www.americanforests.org/

How to Prune Trees
http://willow.ncfes.umn.edu/HT_prune/PRUN001.HTM