@article{PIM_1978_N_S_24_38_a6,
     author = {Ivan Gutman},
     title = {Contribution {To} {The} {Problem} {Of} {The} {Spectra} {Of} {Compound} {Graphs}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {53 },
     year = {1978},
     volume = {_N_S_24},
     number = {38},
     url = {http://geodesic.mathdoc.fr/item/PIM_1978_N_S_24_38_a6/}
}