Resources & Links Resources ISTC User Manual, Version 1.2, released April 2010 (PDF) ONIX for ISTC Overview, revised September 2011 (PDF) ONIX for ISTC XML Schema files, revised October 2011 (XSD) ONIX for ISTC Codelists (HTML) XML-based systems can directly reference a copy of the current schema and code list using the address: http://resource.bowker.com/istc/ONIX_ISTC_Metadata.1.0.1.xsd. This address needs to be included in the XML declaration of each registration request file (as shown in the specification document).