B. J. Balamurugan, K. Thirusangu, D. G. Thomas, and B. J. Murali, “k-Zumkeller Labeling of Graphs”, IJET, vol. 7, no. 4.10, pp. 460–463, Oct. 2018, doi: 10.14419/ijet.v7i4.10.21040.