@article{HellwigVolkmann2013,
  author    = {Angelika Hellwig and Lutz Volkmann},
  title     = {Sufficient conditions for λ′-optimality in graphs of diameter 2},
  journal   = {Discrete mathematics},
  volume    = {Vol. 283},
  number    = {Iss. 1-3},
  pages     = {113 -- 120},
  year      = {2013},
}