1. Anonymous (2003) ISO 16140:2003. International Organization for Standardization, Geneva, Switzerland
2. Anonymous (2005a) ISO 22174:2005. International Organization for Standardization, Geneva, Switzerland
3. Anonymous (2005b) ISO/TS 20836:2005. International Organization for Standardization, Geneva, Switzerland
4. Anonymous (2006a) ISO 20838:2006. International Organization for Standardization, Geneva, Switzerland
5. Anonymous (2006b) ISO 20837:2006. International Organization for Standardization, Geneva, Switzerland