@article{ZR_1997_7_15_a0,
     author = {Bogoljub Stankovi\'c},
     title = {Preface},
     journal = {Zbornik radova},
     pages = {3 },
     publisher = {mathdoc},
     volume = {7},
     number = {15},
     year = {1997},
     url = {http://geodesic.mathdoc.fr/item/ZR_1997_7_15_a0/}
}