Automatic control systems, 7th edition : By Benjamin C. Kuo. Prentice-Hall, Englewood Cliffs, NJ (1995). ISBN 0-13-304759-8. - Weng Khuen Ho; J. R. Zhou (Autom., 1997)

The direct Nyquist array design of PID controllers. - Weng Khuen Ho; Tong Heng Lee; Wen Xu 003; J. R. Zhou; Ee Beng Tay (IEEE Trans. Ind. Electron., 2000)