RFC 5234
Augmented Backus-Naur Form (ABNF), the grammar syntax for parsers generated by APG, is defined here.

RFC 7405
Case-Sensitive String Support in ABNF.

The Internet Engineering Task Force (IETF) Request for Comments (RFC) page. The best place to learn more about the IETF and RFCs. Includes a search page to find them all.

Extract ABNF from RFCs
The ABNF rules are often scattered throughout an RFC document, interspersed with definitions and explanations. This is a very useful tool for extracting all of the ABNF rules into a clean, single file.

GNU General Public Licenses
General Public Licenses, Version 2, Version 3. Used for the C/C++ and Java versions.

BSD-3-Clause License. Used for the JavaScript versions.

OASIS OData Project
The OASIS Open Data Protocol (OData) project is an undertaking for "Simplifying data sharing across disparate applications in enterprise, Cloud, and mobile devices". Thanks to the Technical Committee for using Java APG and contributing three important and useful extensions to it.

SmallMGC is an Open Source Media Gateway Controller for access and residential gateways. APG is the parser of choice for SmallMGC's MEGACO message handling. If you are interested in Next Generation Networks, check out SmallMGC.