Columbia subject headings:
Ammonia--Toxicology--Congresses.
Urea--Metabolism--Disorders--Congresses.
Harvard subject headings:
Ammonia--Toxicology--Congresses.
Urea--Metabolism--Disorders--Congresses.
Princeton subject headings:
Ammonia--Toxicology--Congresses.
Urea--Metabolism--Disorders--Congresses.