@article{PIM_1972_N_S_14_28_a4,
     author = {Drago\v{s} M. Cvetkovi\'c},
     title = {Chromatic {Number} {And} {The} {Spectrum} {Of} {A} {Graph}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {25 },
     publisher = {mathdoc},
     volume = {_N_S_14},
     number = {28},
     year = {1972},
     url = {http://geodesic.mathdoc.fr/item/PIM_1972_N_S_14_28_a4/}
}