N. Davtyan and R. Kamalian, “ON THE NUMBER OF VERTICES WITH AN INTERVAL SPECTRUM IN EDGE LABELING OF REGULAR GRAPHS”, Proc. YSU A: Phys. Math. Sci., vol. 48, no. 3 (235), pp. 40–42, Nov. 2014, doi: 10.46991/PYSUA.2014.48.3.040.