A frequency response function for linear, time-varying systems. - Joseph A. Ball; Israel Gohberg; Marinus A. Kaashoek (Math. Control. Signals Syst., 1995)

Classification of Linear Periodic Difference Equations under Periodic or Kinematic Similarity. - Israel Gohberg; Marinus A. Kaashoek; Johan Kos (SIAM J. Matrix Anal. Appl., 2000)