Nugraha, T., F. A. Noor, M. Abdullah, and K. Khairurrijal. “Density-Functional Study of Electronic Band Structure of Graphene With H2, H, and N Impurities”. Indonesian Journal of Physics, Vol. 21, no. 1, Nov. 2016, pp. 9-13, doi:10.5614/itb.ijp.2010.21.1.2.