Toward time-varying balanced realization via Riccati equations. - J. Imae; J. E. Perkins; John B. Moore (Math. Control. Signals Syst., 1992)

Dynamical Systems that Compute Balanced Realizations and the Singular Value Decomposition. - Uwe Helmke; John B. Moore; J. E. Perkins (SIAM J. Matrix Anal. Appl., 1994)