Columbia subject headings:
Air--Pollution--Environmental aspects--Congresses.
Forest declines--Congresses.
Indicators (Biology)--Congresses.
Plants--Effect of air pollution on--Congresses.
Trees--Wounds and injuries--Congresses.
Harvard subject headings:
Air--Pollution--Environmental aspects.
Forest ecology
Plants--Effect of air pollution on
Princeton subject headings:
Air--Pollution--Environmental aspects.
Forest declines.
Indicators (Biology)
Trees--Effect of air pollution on.
Trees--Wounds and injuries.