1. ISO, ISO 10303–21:2002 Industrial automation systems and integration—Product data representation and exchange: Part 21. Implementation methods: Clear text encoding of the exchange structure.
2. ISO, ISO 10303–11:2004 Industrial automation systems and integration—Product data representation and exchange: Part 11. Description methods: The EXPRESS language reference manual.
3. Information Modeling: The EXPRESS Way;Schenk,1994
4. End User Guide to Industry Foundation Classes;International Alliance for Interoperability,1996