Interior regularity for fractional systems

We study the regularity of solutions of elliptic fractional systems of order 2s, $s\in (0,1)$, where the right hand side f depends on a nonlocal gradient and has the same scaling properties as the nonlocal operator. Under some structural conditions on the system we prove interior Hölder estimates in the spirit of 1]. Our results are stable in s allowing us to recover the classic results for elliptic systems due to S. Hildebrandt and K. Widman 11] and M. Wiegner 19].