1. Safer by design: The management of product design risks under strict liability;Abbott,1988
2. Microprocessor architecture for discrete manufacturing control, Part I: History and problem definition;Alford;IEEE Transactions on Manufacturing Technology,1976
3. Allen Bradley Co. Safety PLCs. (2001). How they differ from their traditional counterparts. White Paper (1755-WP001A-EN-E), Rockwell Automation.
4. Arzen, K.-E., Olsson, R., & Akesson, J. (2002). Grafcet for procedural operator support tasks. In Proceedings of the 15th IFAC congress, Barcelona.
5. Banphawatthanarak, C., Krogh, B. H., & Butts, K. (1999). Symbolic verification of executable control specifications. In Proceedings of the 1999 IEEE conference on computer aided control system design, Hawaii.