1. Ball, J.A., Sasane, A.J.: Extension of the $$\nu $$ -metric. Complex Anal. Oper. Theory 6(1), 65–89 (2012)
2. Bose, N.K.: Multidimensional Systems Theory and Applications, 2nd edn. Kluwer Academic Publishers, Dordrecht (2003) (with contributions by B. Buchberger and J. P. Guiver)
3. El-Sakkary, A.K.: The gap metric: robustness of stabilization of feedback systems. IEEE Trans. Autom. Control 30(3), 240–247 (1985)
4. Hayman, W.K.: Meromorphic Functions. Oxford Mathematical Monographs Clarendon Press, Oxford (1964)
5. Partington, J.R.: Robust control and approximation in the chordal metric. In: Hosoe, S. (ed.) Robust Control. Proceedings of the workshop held in Tokyo. Lecture Notes in Control and Information Sciences, vol. 183. Springer, Berlin (1992)