Hu, J., Yamada, K., Sakanushi, T., Nakui, Y. and Atsuta, Y. (2012) “A Design Method for Control System to Attenuate Periodic Input Disturbances Using Disturbance Observers for Time-Delay Plants”, ECTI Transactions on Electrical Engineering, Electronics, and Communications, 11(1), pp. 37–46. doi: 10.37936/ecti-eec.2013111.170607.