Given a polynomial

which is Hurwitz or

which has zeros only within or on the unit circle, it is of interest to know how much the coefficients t
jcan be perturbed while preserving the stability properties. In this note, a method is presented for obtaining the largest hypersphere centered at
![t^{T} = [t_{1} ... t_{n}]](/images/tex/3372.gif)
containing only polynomials which are stable.