Stability properties of periodic solutions of a Duffing equation in the presence of lower and upper solutions. - Franic Ikechukwu Njoku; Pierpaolo Omari (Appl. Math. Comput., 2003)

On the periodic Ambrosetti-Prodi problem for a class of ODEs with nonlinearities indefinite in sign. - Franco Obersnel; Pierpaolo Omari (Appl. Math. Lett., 2021)

Branches of positive solutions of a superlinear indefinite problem driven by the one-dimensional curvature operator. - Julián López-Gómez; Pierpaolo Omari (Appl. Math. Lett., 2022)