In the paper, the authors consider an object (* plant*)
with a single input $u$ (* control*)
and a single output $x$ (* state*) that is described by
a differential equation
$${d^nx\over dt^n}+b_{n-1}{d^{n-1}x\over dt^{n-1}}+...+b_0=
{d^mu\over dt^m}+a_{m-1}{d^{m-1}u\over dt^{m-1}}+...+a_0,$$
in which there is only one source of
uncertainty in the coefficients $a_i$
and $b_j$:
a parameter $p$ whose value is unknown (but known to belong to an
interval $[p^-,p^+]$) that influences the
coefficients: $a_i=a^{(0)}_i+a^{(1)}_i\cdot p$ and
$b_j=b^{(0)}_j+b^{(1)}_j\cdot p$ (the values $p^-$, $p^+$,
$a^{(0)}_i$, $a^{(1)}_i$, $b^{(0)}_j$, and $b^{(1)}_j$ are known).

The author describes how, given such a system, one can synthesize a controller (i.e., an equation that describes $u$ in terms of $x$) that guarantees the stability of the resulting system of two differential equations for all possible value of the parameter $p\in [p^-,p^+]$.