Columbia subject headings:
Forests and forestry--Symbolic aspects.
Trees--Symbolic aspects.
Harvard subject headings:
Forests and forestry--Symbolic aspects--Congresses.
Trees--Folklore--Congresses.
Trees--Symbolic aspects--Congresses.
Princeton subject headings:
Forests and forestry--Symbolic aspects--Congresses.
Trees--Folklore--Congresses.
Trees--Symbolic aspects--Congresses.