Certification by the International Society of Arboriculture is an important goal and achievement in the career of anyone who works in or around trees.
Complete information about certification -- including exam dates, location, and costs -- can be found on the ISA website.
The Georgia Urban Forest Council offers review courses combined with a test. They may be contacted at: http://www.gufc.org or 470.210.5900.
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Also helpful are the application handbooks produced by the ISA.