http://www.beckett.com
2. Professional Sports Authenticator
http://www.psacard.com
3. Canton Sports Card Report
http://www.cantonsportscardreport.com
4. Sportscard Sheriff
http://www.sportscardsheriff.com
5. eFlipping.com
http://www.eflipping.com
6. Collectionmonster.com
http://www.collectionmonster.com