Oscillation of second-order elliptic equations with damping terms

Some oscillation criteria are given for the second-order elliptic differential equation with damping terms N i,j=1 Di aij (x)Dj y + N i=1 bi(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.  2005 Elsevier Inc. All rights reserved.