Stability and higher integrability of derivatives of solutions in double obstacle problems

Higher integrability of the derivatives of solutions to double obstacle problems associated with the second-order quasilinear elliptic differential equation ∇ · A(x,∇u) = 0 is obtained under natural assumptions on obstacles. This result is used to prove a stability result for solutions to double obstacle problems for varying equations.  2002 Elsevier Science (USA). All rights reserved