1. Li Y, Ang KH, Chong GCY (2006) Patents, software, and hardware for PID control. an overview and analysis of the current art. IEEE Control Syst Mag 26(1):42–54
2. Astrom KJ, Hagglund T (1995) PID controllers: theory, design, and tuning. Instrument Society of America, Research Triangle Park
3. Rhinehart RR, Shinskey FG, Wade HL (2006) Control modes—PID variations. In: Liptak BG (ed) Process control and optimization, 4th edn. Taylor and Francis, Boca Raton, pp 124–130
4. Astrom KJ, Murray RM (2008) Feedback systems an introduction for scientists and engineers. Princeton, Princeton
5. Bryan LA, Bryan EA (1997) Programmable controllers: theory and implementation. Industrial Text Company, Atlanta