Performance and gain and phase margins of well-known PID tuning formulas. - Weng Khuen Ho; O. P. Gan; Ee Beng Tay; E. L. Ang (IEEE Trans. Control. Syst. Technol., 1996)

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)