IETF RFC 2219 (March 1997) Key Words for Use in FRCs to Indoicate Requirement Levels, Bradner, S., ed., < http://www.ietf.org/rfc/rfc2219.txt>
IETF RFC 2616 (June 1999) Hypertext Transfer Protocol - HTTP/1.1, Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and Berners-Lee, T., eds., <http://www.ietf.org/rfc/rfc2616.txt>
IETF RFC 2396 (August 1998) Uniform Resource Identifiers (URI): Generic Syntax , Berners-Lee, T., Fielding, N., and Masinter, L., eds., <http://www.ietf.org/rfc/rfc2396.txt>
OGIS Simple Features Specification for SQL Revision 1.1 (May 1999) Open GIS Consortium Inc. Project Document 99-049 <http://www.opengis.org/docs/99-050.pdf>
OGIS Web Map Service Implementation Specification Version 1.1.1 (January 2002) Open GIS Consortium Inc. Project Document OGC 01-068r3 <http://www.opengis.org/docs/01-068r3.pdf>
OGIS GML Version 3.00 (January 2003) Open GIS Consortium Inc. Project Document OGC 02-023r4 <http://www.opengis.org/docs/02-023r4.pdf>