Columbia subject headings:
Industries--United States--Classification--Indexes.
Industries--United States--Classification.
Occupations--United States--Classification--Indexes.
Occupations--United States--Classification.
United States--Census, 1990.
Harvard subject headings:
Industries--United States--Classification
Industries--United States--Classification--Indexes.
Occupations--United States--Classification
Occupations--United States--Classification--Indexes.
United States--Census, 1990
Princeton subject headings:
Indexes.
Industries--United States--Classification--Indexes.
Industries--United States--Classification.
Occupations--United States--Classification--Indexes.
Occupations--United States--Classification.
United States--Census, 1990.