Oscillation of second order damped elliptic differential equations

We establish some new oscillation theorems for the second order damped elliptic differential equation ∑ i , j = 1 N D i [ a i j ( x ) D j y ] + ∑ i = 1 N b i ( x ) D i y + C ( x , y ) = 0 . Our results are extensions of those for second order ordinary differential equations obtained by Sun [Y.G. Sun, New Kamanev-type oscillation criteria of second order nonlinear differential euqations with damping, J. Math. Anal. Appl. 291 (2004) 341–351].