Signed by David Crosby, Graham Nash, Stephen Stills, and Neil Young .This item comes with a Certificate of Authenticity from a third party authenticator. This Certification of Authenticity does not imply that the item will be certified by any other rival authentication companies. The accompanied certification is the only certification the auction company can confirm. These items are being sold as collectable pieces and there is no guarantee that this item can be resold on any online marketplace. Each of these companies has their own policies and politics.