Abstract
In this paper, oscillation and nonoscillation criteria are established for non-linear neutral delay dierential equations with several positive and negative coecients[x (t) R (t)x (t r)]0+mXi=1Pi (t)Hi (x (t i))nXj =1Qj (t)Hj (x (t j )) = 0:Our criteria improve and extend many results known in the literature. In addition we provethat under appropriate hypotheses, if every solution of the associated linear equation withconstant coecients,y0(t) +mXi=1(pi Xk2 Jiqk)y (t i) = 0 ;oscillates, then every solution of the nonlinear equation also oscillates. KCI Citation Count: 0