@article{ZR_2009_13_21_a0,
     author = {Drago\v{s} Cvetkovi\'c and Ivan Gutman},
     title = {Preface},
     journal = {Zbornik radova},
     pages = {3 },
     publisher = {mathdoc},
     volume = {13},
     number = {21},
     year = {2009},
     url = {http://geodesic.mathdoc.fr/item/ZR_2009_13_21_a0/}
}