Oscillation criteria for second-order nonlinear neutral variable delay dynamic equations. - Hong-Wu Wu; Rong-Kun Zhuang; Ronald M. Mathsen (Appl. Math. Comput., 2006)

Riccati techniques and oscillation for self-adjoint matrix Hamiltonian systems. - Qi-Ru Wang; Yuan-Tong Xu; Ronald M. Mathsen (Comput. Math. Appl., 2009)