Columbia subject headings:
Chimpanzees--Behavior.
Chimpanzees--Psychology.
Gorilla--Behavior.
Gorilla--Psychology.
Mammals--Behavior.
Mammals--Psychology.
Harvard subject headings:
Chimpanzees--Behavior
Chimpanzees--Psychology
Gorilla--Behavior
Gorilla--Psychology.
Mammals--Behavior
Mammals--Psychology.
Princeton subject headings:
Chimpanzees--Behavior.
Chimpanzees--Psychology.
Gorilla--Behavior.
Gorilla--Psychology.
Mammals--Behavior.
Mammals--Psychology.