The method of lower and upper solutions of fourth-order four-point boundary value problems and existence of their positive solutions;

Existence of positive solution for fourth-order four-point Sturm-Liouville boundary value problem

Existnece of concave positive solution for second-order four-point boundary value problem;

Existence and uniqueness of solutions for fourth-order two-point boundary value problems;

The degree theory is applied to obtain an existence theorem for the fourth-order two-point boundary value problem with asymptotic nonlinearity.

The existence of positive solution for a four-order three-point singular boundary value problem;