Oscillation criteria for second order differential equations with positive and negative coefficients

Some oscillation criteria for the second order neutral delay differential equationsx(t)±∑i=1lci(t)x(t-τi)″+∑i=1mpi(t)x(t-δi)-∑i=1nqi(t)x(t-σi)=0,t>0are established. New oscillation criteria are different from one recently established in the sense that the boundedness of the solution in the results of Parhi and Chand [Oscillation of second order neutral delay differential equations with positive and negative coefficients, J. Indian Math. Soc., 66 (1999) 227–235.] has been erased., i.e. we give sufficient conditions for the oscillation of all solutions.