Documentation:
* Architectural options - 5 models: Claddier_Ping.pdf
* The chosen model Trackback / Registry Hybrid: Claddier_Ping_Trackback_Hybrid_Model.pdf
* Technical Spec and Implementation ePublication Archive Citations-Trackback Extension Report (Draft 1).doc
* Requirements - email discussion thread PingMechanismRequirementsDiscussionThread
* Future Work / Ideas from Southampton PingMechanismFutureWork
