School of Mathematical Sciences, Shanxi University, Taiyuan, Shanxi 030006, China
Copyright © 2010 Weiping Yan and Jurang Yan. This is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
For a neutral differential equation with positive and changeable sign
oscillation criteria are established, where q(t) is not required as nonnegative. Several new results are obtained.