United States Patent and Trademark Office. Office of Documention Planning and Support, and Control. text Washington, D.C U.S. Dept. of Commerce, Patent and Trademark Office, Search znd Information Resources For sale by the Supt. of Docs., G.P.O monographic Description based on: Dec.1992, basic manual. Patents United States Classofication Periodicals C 21.12: C 21.12: http://purl.access.gpo.gov/GPO/LPS47620 http://purl.access.gpo.gov/GPO/LPS47620 20160527183616.0 299464