1. J. Helly, San Diego Bay Project, 1998, http://sdbay.sdsc.edu.
2. B.R. Schatz, Information retrieval in digital libraries: bringing search to the net, Science, 1980.
3. PURL, Dublin Core Metadata, 1998, http://purl.org/metadata/bublin_core.
4. http://www.w3.org/RDF, ‘Resource Description Framework (RDF) Model and Syntax Specification, W3C Working Draft 19 August 1998’, W3C.
5. http://www.fgdc.gov/metadata/contstan.html, ‘Content Standard for Digital Geospatial Metadata (CSDGM)’, Federal Geographic Data Committee, 1988.