Atta, Soumen, et al. “No-Hole λ-L (k, K – 1, …, 2,1)-Labeling for Square Grid”. Bulletin de la Société Des Sciences et Des Lettres de Łódź, vol. 67, no. 3, Apr. 2017, pp. 9-19, https://doi.org/10.26485/0459-6854/2017/67.3/1.