Hefnawy A.I., Elsid E.A., and Euat Tallah S. “Cordial Labeling for the Sum and Union of the Second Power of Paths and Stars”. Utilitas Mathematica 108 (September 9, 2018). Accessed May 8, 2026. https://utilitasmathematica.com/index.php/Index/article/view/1294.