Anderson, B. D. O.Jury, E. I.2026-01-012026-01-010005-1098ORCID:/0000-0002-1493-4774/work/174740278https://hdl.handle.net/1885/733799737Youla, Bongiorno and Lu have presented a condition for the stabilizability using stable controllers of an unstable plant. We show this condition may be reformulated in terms of Cauchy indices, allowing its checking in a finite number of rational operations, should the plant not be given in factored form, i.e. should its poles and zeros be unknown. The results applies to discrete and continuous-time, and scalar and multivariable plants.en197610.1016/0005-1098(76)90060-133747029805