@article{NAM_1922_5_1__340_0,
     author = {Lebesgue, Henri},
     title = {Sur les cercles focaux},
     journal = {Nouvelles annales de math\'ematiques : journal des candidats aux \'ecoles polytechnique et normale},
     pages = {340--350},
     publisher = {Carilian-Goeury et Vor Dalmont},
     volume = {5e s{\'e}rie, 1},
     year = {1922},
     language = {fr},
     url = {http://www.numdam.org/item/NAM_1922_5_1__340_0/}
}