| GPSF Services- | On-Line Pricing Sources |
| Detailed Service | Internet Link |
| Books | |
| Alibris.Com | http://www.alibris.com/ |
| Bibliofind.Com | http://www.bibliofind.com/ |
| Advanced Book Exchange | http://www.abebooks.com/ |
| Barnes and Noble(See Network Books) | http://www.bn.com/ |
| A1 Books | http://www.a1books.com/ |
| Borders Inc (Books) | http://www.borders.com/ |
| Amazon.Com | http://www.amazon.com/ |
| Stamps | |
| American Philatelic Society Stamp Store | http://www.stampstore.org/ |
| Whoesale/Retail Price Guides | |
| LW Books | http://www.lwbooks.com/ |
| Collector Books | http://www.collectorbooks.com/ |
| Krause Publications | http://www.krause.com/ |
| The Charlton Press | http://www.charltonpress.com/ |