... constant independent of handz(x),IlvilL =llvll~,w+II'Vvllo,wl, Ilvllo,w== ~II'Vvll~,wl==('Vv, 'Vv)', 'Vv(x(±o.S;))== vi~ o.S;)forx(±o.s;)Ew:,o(u, v)is ... in Mathematical Physic, Mir., Moscow, 1979.Received May18, 1999Revised April 26,2000Institute of Mathematics, Hanoi, Vietnam. T,!-p chI Tin liocvaDi'eukhien hoc, T.16, S.2(2000), ... media, SIAMJ.Numer. Anal. 34 (1) (1997) 201-227.[2] Dang Quang A, Approximate method for solving an elliptic problem with discontinuous coef-ficients,J.of Camp. and Applied Math.51(1994)...