- Nitrogen--Fixation--Congresses (3)
- Bacterial genetics (1)
- Enzymes--Congresses (1)
- Micro-organisms, Nitrogen-fixing--Congresses (1)
- Microbial genetics--Congresses (1)
- Molybdenum--Metabolism--Congresses (1)
- Molybdenum--Physiological effect--Congresses (1)
- Nitrogen--Fixation (1)
- Nitrogen-fixing microorganisms (1)
- Nitrogen-fixing microorganisms--Congresses (1)
- Plant genetics--Congresses (1)
- Plant-microbe interrelationships--Congresses (1)