Columbia subject headings:
Harvard subject headings:
Communicable diseases--Transmission
Diseases--Causes and theories of transmission.
Environmental toxicology.
Refuse and refuse disposal--Health aspects.
Sewage--Microbiology
Princeton subject headings:
Communicable diseases--Transmission.
Diseases--Causes and theories of causation.
Environmental toxicology.
Refuse and refuse disposal--Health aspects.
Sewage--Microbiology.