The Application Exchange (APEX) Access Service - (IETF RFC 3341) describes the Application Exchange (APEX) access service, addressed as the well-known endpoint "apex=access" and used to control use of both the APEX "relaying mesh" and other APEX services, Marshall T. Rose, Graham Klyne and David H. Crocker, July 2002
The Application Exchange Core - (IETF RFC 3340) describes Application Exchange (APEX) Core, an extensible, asynchronous message relaying service for application layer programs, Marshall T. Rose, Graham Klyne and David H. Crocker, July 2002
The Application Exchange (APEX) Option Party Pack, Part Deux! - (IETF RFC 3342) describes Application Exchange (APEX) Core, defines various options to change the default behavior of APEX's "relaying mesh," Graham Klyne, Marshall T. Rose, Michael F. Schwartz, Eric Dixon, Huston Franklin, Jay Kint, Darren New and Scott Pead, July 2002