1. Ball, J.A., Gohberg, I and Rodman, L.: Minimal factorization in terms of spectral data, Integral Equations and Operator Theory, 10 (1987), 309–348.
2. Ball, J.A. and Helton, J.W.: A Beurling-Lax theorem for the Lie group U(m,n) which contains most classical interpolation theory, J. Operator Theory 9 (1983), 107–142.
3. Ball, J.A. and Helton, J.W.: Beurling-Lax representations using classical Lie Groups with many applications II: GL(n,(math)) and Wiener-Hopf factorization, Integral Equations and Operator Theory 7(1984), 291–309.
4. Ball, J.A. and Ran, A.C.M.: Hankel norm approximation of a rational matrix function in terms of its realization, in Modelling, Identification and Robust Control, C.I. Byrnes and A. Lindquist (eds.), North Holland, 1986, 285–296.
5. Ball, J.A. and Ran, A.C.M.: Optimal Hankel norm model reductions and Wiener-Hopf factorization I: The canonical case, SIAM J. Control and Opt. 25 (1987), 362–382.