1. www.gigapedia.org
2. www.ebook.com.vn
3. http://www.ebook.edu.vn
4. http://ebook.edu.net.vn/
5. http://srdata.nist.gov/gateway
6. http://www.scielo.br
7. http://www.diesel sinh học.org.au
8. http://www.greenfuels.org/emissionimpact.html
9. www.Elsbett.de34025
10. http://votauthuy.org