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2. GELB , A. , VAN DEB VELDE , W. , 1968 ,Multiple–;Input Describing Functions and Nonlinear System Design( New York McGraw–Hill ), Chap. 9 , pp. 481 – 484 .
3. HOROWITZ , I , 1963 ,Synthesis of Feedback Systems( New York Academic Press ), Chap. 7 , pp. 334 – 337 .
4. Optimum synthesis of non-minimum phase feedback systems with plant uncertainty†
5. SAUCEDO , R. , and SCHIKING , E. , 1968 ,Introduction to Continuous and Digital Control Systems( New York MacMillan ), pp. 419 –; 424 and 497 –; 506