1.    (with K.-H. Förster) On nonnegative realizations of rational matrix functions and nonnegative input-output systems, pp. 89-104 in: Operator Theory: Advances and Applications, Vol. 103, Birkhauser Verlag, Basel, 1998. MR 99f:93022.

 

2.    Periodic groups of operators in Banach spaces, Proc. Amer. Math. Soc., 126 (1998), 1433-1444. MR 98j:47081.

 

3.    (with K.-H. Förster) The index of triangular operator  matrices, Proc. Amer. Math. Soc., 128 (2000), 1167-1176. MR 2000i:47003.

 

4.    (with K.-H. Förster) Nonnegative realizations of  matrix transfer functions, Lin. Algebra Appl., 311 (2000), 107-129. MR 2001b:93014.

 

5.    (with J. Zemánek) A resolvent condition implying power  boundedness, Studia Math. (Warszawa), 134 (1999), 143-151.