Yongdong Zhao and Suhada Jayasuriya, "A frequency domain
criterion for robustly stabilizing a family 
of interval plants", <I> Transactions of the ASME</I>, 1995, Vol. 117,
pp. 98-104.
<P>

Yongdong Zhao and Suhada Jayasuriya, "Frequency domain
criteria for synthesizing robustly stabilizing compensators for a
class of interval plants", <I> Journal of Dynamical Systems,
Measurement, and Control</I>, 1995, Vol. 117, pp. 241-247.
<P>

New control methods are proposed for stabilizing a system 
$${d^nx\over dt^n}+b_{n-1}{d^{n-1}x\over dt^{n-1}}+...+b_0=
{d^mu\over dt^m}+a_{m-1}{d^{m-1}u\over dt^{m-1}}+...+a_0$$ 
($x$ - state, $u$ - control), 
in which the values $b_i$ that describe the dependency on the control
are known precisely, while for the values $a_i$ that describe the
"inertia" of the system (i.e., its dependence on the past states) we
only know {\it intervals} of possible values.