OSCILLATION CRITERIA FOR NONLINEAR SECOND ORDER ELLIPTIC DIFFERENTIAL EQUATIONS

The second order elliptic differential equations $$ L_1(y;x)=\sum_{i,j=1}^{n}D_i [A_{ij}(x)D_j y]+p(x)f( y) = 0 \tag {1.1} $$ and $$ L_2(y;x)=\Delta y+p(x)|y|^{\gamma}\roman{sign} y=0,1\not =\gamma>0 \tag{1.2} $$ are considered in an exterior domain $\Omega\subset R^n $ , $n\geq 2 $, where $ p $ can chang sign. Some new sufficient conditions for the oscillation of solutions of (1.1) and (1.2) are established.