Patent Database
- Deutschen patent- und Markenamtes: https://depatisnet.dpma.de
- Indian Patent Database: http://www.indianpatents.org.in/db/db.htm
- European Patent: Esp@cenet: http://worldwide.espacenet.com/
- Google Patent Search: http://www.google.com/patents/
- U. S. Patent and Trademark Office: http://www.uspto.gov/patents/index.jsp