@article{CMH_1988__63_4_140117,
     author = {B., Colin de Verdi\`ere de Colbois},
     title = {Sur la multiplicit\'e de la premi\`ere valeur propre d'une surface de {Riemann} \`a courbure constante.},
     journal = {Commentarii mathematici Helvetici},
     pages = {194--208},
     publisher = {mathdoc},
     volume = {63},
     number = {4},
     year = {1988},
     zbl = {0656.53043},
     url = {http://geodesic.mathdoc.fr/item/CMH_1988__63_4_140117/}
}