http://www.rfc-editor.org/rfc/rfc7405.txt
RFC 7405: Case-Sensitive String Support in ABNF, P. Kyzivat2014-12-01T23:00:00-00:00This document extends the base definition of ABNF (Augmented Backus-Naur Form) to include a way to specify US-ASCII string literals that are matched in a case-sensitive manner.