  For systems of linear differential equations on a compact interval, we
investigate the~dependence on a parameter $\varepsilon$ of the solutions to
boundary-value problems in the Sobolev spaces $W^{n}_{\infty}$. We obtain a
constructive criterion of the continuous dependence of the solutions of these
problems on the~parameter $\varepsilon$ for $\varepsilon=0$. The degree of
convergence of these solutions is established.
