Columbia subject headings:
Harvard subject headings:
Nitrogen-fixing microorganisms--Congresses.
Phytopathogenic microorganisms--Congresses.
Plant-microbe relationships--Congresses.
Plants--Microbiology--Congresses.
Princeton subject headings:
Nitrogen-fixing microorganisms--Congresses.
Phytopathogenic microorganisms--Congresses.
Plants--Microbiology--Congresses.