1.
Li J, Luo J, Wang Z. RETRACTED ARTICLE: Periodic Solutions of Second Order Impulsive Differential Equations at Resonance via Variational Approach. MMA [Internet]. 2014Nov.1 [cited 2024Nov.22];19(5):664-75. Available from: https://jest.vgtu.lt/index.php/MMA/article/view/3330