We consider quadruples of matrices (E,A,B,C) defining generalized linear
multivariable time-invariant dynamical systems, with E,A square matrices
and B, C rectangular matrices.
Using geometrical techniques we present upper bounds and lower bounds for
the distances between a quadruple and the nearest structurally unstable,
uncontrollable and/or unobservable one, in terms of the singular values of
matrices associated to the quadruple.