Green's functions and spectral theory for the Hill's equation. - Alberto Cabada; José Ángel Cid; Lucía López-Somoza (Appl. Math. Comput., 2016)

Constant-Sign Green's Function of a Second-Order Perturbed Periodic Problem. - Alberto Cabada; Lucía López-Somoza; Mouhcine Yousfi (Axioms, 2022)