New approaches for observer design in linear matrix second order systems. - Seung-Keon Kwak; Rama K. Yedavalli (ACC, 2000)

Observer design in matrix second order system framework; measurement conditions and perspectives. - Seung-Keon Kwak; Rama K. Yedavalli (ACC, 2000)

Stability, controllability and observability criteria for the 'reciprocal state space framework'. - Yuan-Wei Tseng; Seung-Keon Kwak; Rama K. Yedavalli (ACC, 2003)