“…In the standard system theory, there are many studies related to the simultaneous stabilization problem. As representative works on this issue, we can cite the references [1], [2], [3], [4], [5], [7], [8], [9], [17], [19]. Particularly, as stated in [2], it was shown that the simultaneous stabilizability of three linear systems is rationally undecidable, that is This work is not supported by any organizations All of the authors are with Graduate School of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka, 560-8531, Japan kaneko@ft-lab.sys.es.osaka-u.ac.jp to say, it is not possible to find necessary and sufficient conditions for the simultaneous stabilization of three linear systems in the sense that there exist no ways for checking the simultaneous stabilizability by algebraic, logical, and sign test operations.…”