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2. Gu, P. H. and Chan, K., 1995, Product modelling using STEP, Computer-Aided design, 27, 163–179.
3. ISO, 1994a, Industrial automation systems and integration: Product data representation and exchange: Part 11: Description methods: The EXPRESS language reference manual, Reference number: ISO 10303-11:1994(E). 1st edition, Switzerland.
4. ISO, 1994b, Industrial automation systems and integration: Product data representation and exchange: Part 203: Application protocol: Configuration controlled 3D designs of mechanical parts and assemblies, Reference number: ISO 10303-203:1994(E). 1st edition, Switzerland.
5. ISO, 1998, Industrial automation systems and integration: Product data representation and exchange: Part 45: Integrated generic resource: Materails, Reference number: ISO 10303-45:1998(E). 2nd edition, Switzerland.