Columbia subject headings:
Middle Older people men--United States.
Middle Older people women--United States.
Middle-aged men--United States.
Middle-aged women--United States.
Older people--United States.
Harvard subject headings:
Middle-aged men--United States.
Middle-aged women--United States.
Older people--United States.
Princeton subject headings:
Adulthood.
Middle age.
Old age.