1. An example is provided by Hosoya 2005, Regular expression types for XML.
2. Denning 1978, Machines, Languages, and Computation, p. 161.
3. For instance, Regular expression, http://en.wikipedia.org/wiki/Regular_expression#Syntax.
4. Garshol 2003, BNF and EBNF, http://www.garshol.priv.no/download/text/bnf.html#id2.3.
5. Anderson 2004, CL-XML: Common Lisp support for the’ Extensible Markup Language, links examples of BNF used in XML parsers. See http://pws.prserv.net/James.Anderson/XML/.