Fredholm theory connected with a Douglis–Nirenberg system of differential equations over an exterior region in Rn

We consider a boundary problem over an exterior subregion of Rn for a Douglis–Nirenberg system of differential operators under limited smoothness asumptions and under the assumption of parameter‐ellipticity in a closed sector L in the complex plane with vertex at the origin. We pose the problem in an Lp Sobolev–Bessel potential space setting, 1