... clla u ti;lix Ihcn hlt'dng clia vecW u , vdi u la philp vecW don V!hlt'dng ngoai clia bien an, 4) Cfllt tllicll Phlt'dng lrlnh Laplace IllY la plHfl1ng trlnh d~1Oham rieng cd b,ln nhlt'ng ra't ... K={x,y} Iii t~p compacL tmng Q 1\p dl,lng djnh 19 Harnack(djnh hang s6 C E( 1,0) Lhoa "dI11E N 19 1I1 .4- chlrdng I) dol vdi K ,t6n t~i , C vlllx) < vlIlY) SlIY C(UlIlX)-lIl(X)+I) < ulI,(Y)-UI(Y)+1 C(uII1(x)-ul(x)+I) ... toy y lrang Q c6 dinh xEK 1'6n L1,(ll'll-llj)(Y)::; -(UII1-Uj)(X) c I...