Li J, Luo J, Wang Z. Retraction notice to “Periodic Solutions of Second Order Impulsive Differential Equations at Resonance via Variational Approach” [Math. Model. Anal. 19(5):664–675, 2014]. MMA [Internet]. 2015Mar.30 [cited 2024Dec.22];20(2):289. Available from: https://journals.vilniustech.lt/index.php/MMA/article/view/1000