Index to the U. S. patent classification.
APA Citation
United States. Patent and Trademark Office. Index to the U. S. patent classification. [Washington]: U.S. Dept. of Commerce, Patent and Trademark Office.
MLA Citation
United States. Patent and Trademark Office. Index to the U. S. Patent Classification. [Washington]: U.S. Dept. of Commerce, Patent and Trademark Office,
Warning: These citations may not always be complete (especially for serials).