Cao Ting-Bin and Liu Kai and Xu Hong-Yan: Bounds for the sums of zeros of solutions of u(m) = P(z)u where P is a polynomial. (2011)
Tu Jin and Xu Hong-Yan and Zhang Cui-Yan: On the zeros of solutions of any order of derivative of second order linear differential equations taking small function. (2011)
Xu Hong-Yan and Cao Ting-Bin: Oscillation of solutions of some higher order linear differential equations. (2009)