References
==========

`RFC 2119: Key words for use in RFCs to Indicate Requirement
Levels <http://www.ietf.org/rfc/rfc2119.txt>`_ (March 1997)

`Extensible Markup Language (XML) 1.0 (Fourth
Edition) <http://www.w3.org/TR/2006/REC-xml-20060816/>`_ (16 August 2006)

`XML Information Set (Second
Edition) <http://www.w3.org/TR/2004/REC-xml-infoset-20040204/>`_ (4
February 2004)

`Namespaces in XML (Second
Edition) <http://www.w3.org/TR/2006/REC-xml-names-20060816/>`_ (16 August
2006)

`Resource Description Framework (RDF): Concepts and Abstract
Syntax <http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/>`_ (10
February 2004)

`RDF/XML Syntax Specification
(Revised) <http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/>`_
(10 February 2004)

`Mathematical Markup Language (MathML) Version 2.0 (Second
Edition) <http://www.w3.org/TR/2003/REC-MathML2-20031021/>`_ (21 October
2003)

`XML Linking Language (XLink) Version
1.0 <http://www.w3.org/TR/2001/REC-xlink-20010627/>`_ (27 June 2001)