Oscillation of second-order elliptic equations with damping terms

Some oscillation criteria are given for the second-order elliptic differential equation with damping terms∑i,j=1NDi[aij(x)Djy]+∑i=1Nbi(x)Diy+C(x,y)=0,x∈Ω(r0). The results are extensions of modified Riccati technique and include earlier results of Noussair and Swanson, Xu, and Zhang et al.