United States Patent and Trademark Office

or claims; and limited by date. Pre-grant publication of patent applications, a new information product since spring of 2001, can be searched in the same way. In addition to searching patents by field and patent number, the agency offers searching by U.S. Patent Classification (http://www.uspto.gov/go/ classification/). This system has been in use for over 100 years, but has been subject to nearly constant revision and amendment to keep it up to date. A classification search offers the advantage of bringing together patents that have specific features in common, regardless of the language used to describe those features, which is a challenge when searching by keyword. Once a class and subclass are selected, the system provides a complete and current list of all patents associated with that classification. The searcher can then click on the patent number to view the image. World Wide Web Reviews 49