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NTPA: National Trade and Professional Associations of the United States
Call Number: HD 2425 .D53
This directory covers about 7,500 national trade associations, labor unions, professional, scientific, or technical societies, and other national organizations."
Small Business Sourcebook
Call Number: HD 2346 .U5 S66
For 200+ types of businesses, lists associations, other organizations of interest, reference works, statistical sources, trade shows, and franchises.