@article{PIM_1977_N_S_21_35_a28,
     author = {B. Stankovi\'c},
     title = {Approximate {Solutions} {Of} {The} {Operator} {Linear} {Differential} {Equation} {I}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {185 },
     publisher = {mathdoc},
     volume = {_N_S_21},
     number = {35},
     year = {1977},
     url = {http://geodesic.mathdoc.fr/item/PIM_1977_N_S_21_35_a28/}
}