Xu Fuyi: Three symmetric positive solutions of fourth-order nonlocal boundary value problems. (2011)
Xu Fuyi: Multiple positive solutions of nonlinear singular m-point boundary value problem for second-order dynamic equations with sign changing coefficients on time scales. (2010)
Xu Fuyi: The existence of positive solutions for nonlinear boundary system with p-Laplacian operator based on sign-changing nonlinearities. (2010)