Columbia subject headings:
Harvard subject headings:
Electronic commerce--Directories.
Electronic commerce--Statistics.
Internet industry--Directories.
Internet industry--Statistics.
Online information services industry--Directories.
Online information services industry--Statistics.
Web sites--Directories
Web sites--Statistics.
Princeton subject headings:
Directories.
Internet industry--Directories.
Internet industry--Statistics.
Online information services industry--Directories.
Online information services industry--Statistics.
Web sites--Directories.
Web sites--Statistics.