@article{NAM_1862_2_1__315_1,
     author = {Beltrami},
     title = {Extrait d'une lettre},
     journal = {Nouvelles annales de math\'ematiques : journal des candidats aux \'ecoles polytechnique et normale},
     pages = {315--316},
     publisher = {Carilian-Goeury et Vor Dalmont},
     volume = {2e s{\'e}rie, 1},
     year = {1862},
     language = {fr},
     url = {http://www.numdam.org/item/NAM_1862_2_1__315_1/}
}