Columbia subject headings:
Government information--United States--Directories.
Information services--United States--Directories.
Science--Information services--Directories.
Technology--Information services--Directories.
Harvard subject headings:
Information services--United States--Directories
Science--Information services--Directories
Technology--Information services--Directories
Princeton subject headings:
Directories.
Government information--United States--Directories.
Information services--United States--Directories.
Science--Information services--Directories.
Technology--Information services--Directories.