Nooraldeen .O. AL-saklady, and Mahioub .M. Q. Shubatah. “The 2-Domination Number in Interval-Valued Fuzzy Graphs”. IJRDO -JOURNAL OF MATHEMATICS, Vol. 6, no. 3, Mar. 2020, pp. 13-30, doi:10.53555/m.v6i3.3535.