@article{PIM_1979_N_S_26_40_a18,
     author = {Jovan D. Ke\v{c}ki\'c},
     title = {On {Nonlinear} {Superposition,} {III}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {131 },
     year = {1979},
     volume = {_N_S_26},
     number = {40},
     url = {http://geodesic.mathdoc.fr/item/PIM_1979_N_S_26_40_a18/}
}