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Business, Science & Technology Center

Common Law Trademark Sources


What are trademarks?
According to the U.S. Patent and Trademark Office, a trademark is a “word, name, symbol or device which is used in trade with goods to indicate the source of the goods and to distinguish them from the goods of others.”

What is the difference between registered trademarks and unregistered trademarks?
Some trademark owners register their marks with the U.S. Patent & Trademark Office. Registered trademarks are indicated by the symbol “®,” and allow certain rights in interstate and foreign commerce.

The first business to use a trademark generally obtains certain common law rights to it, whether or not it is registered. The owners of unregistered trademarks may indicate their claim to common law rights to the trademark by using “TM” with it.

You'll find more background information on trademarks on the Librarian's Index to the Internet Patents and Trademark page.

What is a common law trademark search?
A common law trademark search involves checking directories, databases and other sources to see whether a given trademark has been used already, meaning someone may have common law rights to it.

A common law trademark search is generally done after searching the USPTO database of registered trademarks. The USPTO database can be searched in the library's Patent & Trademarks Center.

Why is it a good idea to do a "common law" trademark search on the name I want to use for my company / product / service / band?
If you want to register your trademark, the federal trademark application requires a signed declaration from the applicant that "to the best of his/her knowledge no other person, firm, corporation, or association has the right to use the above identified mark…"
Legal considerations aside, it is good business sense to create a unique name or logo that identifies your product or service.


What are some sources I can check at San Francisco Public Library?
Following is a list of some of the major types of sources one can consult in doing a common law trademark search.

Unless noted otherwise, all sources are located in the Business, Science & Technology Center.

General Sources of Business Names

A business name is not in itself a trademark. But it is still useful to search general business directories to find out what names are in use.

  • Dun & Bradstreet Million Dollar Directory
  • Ward's Business Directory of U.S. Private & Public Companies
  • Thomas Register of American Manufacturers & Thomas Register Catalog File - contains an index to trade names as well as manufacturer's listings. Also available through the Thomas Register Web site.
  • Consultants & Consulting Organizations Directory
  • Encyclopedia of Associations - good source for non-profit and special interest organizations. In print and through SFPL Online via Galenet (Associations Unlimited).
  • ReferenceUSA - contains 12 million business names. It is searchable by any keyword in the name and also by industry and location.
  • D&B International Business Locator - contains 28 million company names from 200 countries around the world

California Business Search

Access to more than two million records filed in the State of California's corporation, limited partnership and limited liability company databases.

California Business Portal

Fictitious Business Name Search

The law requires every person who transacts a business for profit under a fictitious business name to file a statement in the county of the principal place of business within 40 days from the time such business commences. The statement expires in 5 years and a new filing is required upon expiration. Fictitious Business Name Statements are required to ensure that consumers have access to the true name and address of the owners of a business.

San Francisco Fictitious Business Name Search

Directories of Local Businesses

[See Local Company Research Resources for a more complete list of local sources]

  • California Manufacturers Register
  • Directory of California Wholesalers & Service Companies
  • Dun's Regional Business Directory

General Sources of Brand & Product Names

  • Brands & Their Companies - international and U.S. listings
  • The Advertising Red Books (formerly “Standard Directory of Advertisers”) - brands and advertisers are indexed by industry and location.

Sources for Specific Goods & Services

A selected list of some of the better known resources. The Business, Science & Technology Center has hundreds of trade directories for a wide range of industries.

  • CorpTech Directory of Technology Companies - high-tech companies and products. On CD-Rom and in print.
  • Data Sources - software products & companies
  • RN & WPL Encyclopedia - best source for identifying clothing labels and manufacturers
  • Sweet's Catalog - many volumes of building and construction products

Where to find Band Names

A short list of resources in the Art, Music & Recreation Center

Print Sources
  • All-Music Guide
  • Trouser Press Guide to New Wave Record Reviews
  • Music Index - yearly index to magazine articles
Web Sites

Additional suggestions

  • Search the Internet for your prospective trademark. Use a search engine like Google for a broad search or use an index such as Yahoo to concentrate on a business or product category.
  • Scan trade magazines for business and product names. Business Publication Advertising Source from Standard Rate & Data Service is an excellent source of industry publications.
  • Consult local and regional yellow pages.
  • There are companies that perform trademark searches for a fee. They can be located in the phone book under “trademark consultants,” or found online in library databases such as Reference USA.


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