@article{10_2298_TAM1501027J,
     author = {Vladimir Jovanovi\'c},
     title = {A note on the proof of {Bertrand's} theorem},
     journal = {Theoretical and applied mechanics},
     pages = {27 },
     publisher = {mathdoc},
     volume = {42},
     number = {1},
     year = {2015},
     doi = {10.2298/TAM1501027J},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.2298/TAM1501027J/}
}