@article{JMPA_1848_1_13__231_0,
     author = {Bertrand, J.},
     title = {Sur un cas remarquable de tautochronisme},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {231--232},
     year = {1848},
     publisher = {Gauthier-Villars},
     volume = {1e s{\'e}rie, 13},
     language = {fr},
     url = {https://www.numdam.org/item/JMPA_1848_1_13__231_0/}
}