Interior $L_p$ regularity for Stokes systems

A new iteration method is represented to study the interior $L_p$ regularity for Stokes systems both in divergence form and in non-divergence form. By the iteration, we improve the integrability of derivatives of solutions for Stokes systems step by step; after infinitely many steps, $L_p$ regularity is achieved; and in each step, the maximal function method is used where solutions and their derivatives are involved simultaneously in each scale. The Hölder continuity of the coefficients in spatial variables is assumed to compensate the different scalings between the solutions and their derivatives.