@article{PIM_1990_N_S_48_62_a16,
     author = {P. S. Milojevi\'c},
     title = {Solvability {Of} {Operator} {Equations} {And} {Periodic} {Solutions} {Of} {Semilinear} {Hyperbolic} {Equations}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {133 },
     year = {1990},
     volume = {_N_S_48},
     number = {62},
     url = {http://geodesic.mathdoc.fr/item/PIM_1990_N_S_48_62_a16/}
}