International Society of Arboriculture: The International Society of Arboriculture is a worldwide professional organization dedicated to fostering a greater appreciation for trees and to promoting research, technology, and the professional practice of arboriculture.

Oregon Construction Contractors Board: The Oregon Construction Contractors Board is a State agency that protects consumers by regulating construction-contracting businesses.

Portland Parks and Recreation Department of Urban Forestry: This site contains information on obtaining permits for tree pruning, removal and planting both on public and private land.

City of Portland Tree Regulations: View the City of Portland street tree regulations. Know the law before you cut.

Friends of Trees: Friends of Trees is a local non-profit organization dedicated to bringing people in the Portland-Vancouver metro area together to plant and care for city trees and green spaces.