Columbia subject headings:
American newspapers--Directories.
American periodicals--Directories.
Canadian newspapers--Directories.
Canadian periodicals--Directories.
Harvard subject headings:
American newspapers--Directories
American periodicals--Directories.
Canadian newspapers--Directories
Canadian periodicals--Directories.
Princeton subject headings:
American newspapers--Directories.
American periodicals--Directories.
Canadian newspapers--Directories.
Canadian periodicals--Directories.
Directories.