1. Coughanowr , D. R. ( 1991 ) Process Systems Analysis and Control, , II edn. McGraw Hill Inter . edn. , New York , pg . 271 .
2. Refinements of the Ziegler–Nichols tuning formula
3. Seborg , D. E.
Edgar , T. F. and
Mellichamp , D A. ( 1989 ) Process Dynamics and Control, , JohnWiley & Sons , NewYork , pg . 282 .