1. The past of PID controllers;Bennett,2000
2. A reference guide to PID controllers in the nineties;Lelic,2000
3. The future of PID control;Åström;Control Engineering Practice,2001
4. Advanced PID Control, ISA – The Instrumentation, Systems, and Automation Society;Åström,2006
5. Optimum settings for automatic controllers;Ziegler;ASME Transactions,1942