KUO, Chung-Cheng. “Perturbations of Local C-Cosine Functions”. Studia Universitatis Babeș-Bolyai Mathematica 65, no. 4 (November 28, 2020): 585–597. Accessed January 19, 2026. https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/2611.