@article{PIM_1976_N_S_20_34_a7,
     author = {D. M. Cvetkovi\'c and I. B. Lackovi\'c and S. K. Simi\'c},
     title = {Graph {Equations,} {Graph} {Inequalities} {And} {A} {Fixed} {Point} {Theorem}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {59 },
     publisher = {mathdoc},
     volume = {_N_S_20},
     number = {34},
     year = {1976},
     url = {http://geodesic.mathdoc.fr/item/PIM_1976_N_S_20_34_a7/}
}