Here are some relevant subject headings to search in Tripod from the Browse Books & More page:
Antitrust law
Barriers to entry (industrial organization)
Big business
Cartels
Competition
Consumer protection
Corporations -- corrupt practices
[Geographic area] -- Economic policy
Free trade
Industrial concentration
Industrial organization
Industrial policies
Industries -- [Geographic area]
Markets [or various industry names] -- Law and Legislation
[various industries] -- Mergers
Monopolies
Monopolistic competition
Oligopolies
Price discrimination
Restraint of Trade
Trade regulation
Trusts, industrial
add "-- [your Geographic area of interest]" to any of the above subject headings to look for results specific to your area of interest.