1. M. A. Naimark, Linear Differential Operators, Ungar, New York, 1967.
2. E. A. Coddington, and N. Levinson, Theory of Ordinary Differential Equations, Krieger Pub. Co., New York, Toronto, London, 1955.
3. Existence results for a linear equation with reflection, non-constant coefficient and periodic boundary conditions
4. Solutions and Green’s function of the first order linear equation with reflection and initial conditions
5. On a new method for constructing the Green function of the Dirichlet problem for the polyharmonic equation