Columbia subject headings:
Harvard subject headings:
Electricity--Social aspects.
Mass media--Philosophy
Mass media--Technological innovations
McLuhan, Marshall, 1911-1980
McLuhan, Marshall, 1911-1980--Knowledge--Mass media.
Telecommunication--Technological innovations
Telegraph--Social aspects.
Princeton subject headings:
Electricity--Social aspects.
Mass media--Philosophy.
Mass media--Technological innovations.
McLuhan, Marshall, 1911-1980.
Telecommunication--Technological innovations.
Telegraph--Social aspects.