1. ISO DIS 10303-1 (1993) Product Data Representation and Exchange ? Part I: Overview and Fundamental Principles, ISO TC184: Industrial Automation Subcommittee 4: Industrial Data and Global Manufacturing Programming Languages, N193, 26 March
2. ISO DIS 10303-1 (1992) Product Data Representation and Exchange ? Part 11: The EXPRESS Language Reference Manual, ISO TC184: Industrial Automation, Subcommittee 4: Industrial Data and Global Manufacturing Programming Languages, N151, 31 August
3. McKay, A. (1992) Application Interpretation Requirements Version 3, ISO TC184/SC4/WG4 N37, 10 January
4. ISO DIS 10303-1 (1993) Product Data Representation and Exchange ? Part 21: Implementation Methods Clear Text Encoding of the Exchange Structure, ISO TC184: Industrial Automation, Subcommittee 4: Industrial Data and Global Manufacturing Programming Languages, N204, 28 May
5. Burkett, W.C.; Yang, Y. (1992) On the implementation of STEP, ISO TC184/SC4/WG4 N68, October