Published in Compte Rendu, in 1880, in volume 90, pages 1579-1580

Published in Compte Rendu, in 1880, in volume 91, pages 436-439

Published in Comptes rendus hebdomadaires des séances de l'Académie des sciences, in 1880, in volume 91, pages 1034-1038

Published in Compte Rendu, in 1880, in volume 91, pages 1094-1095