@article{NUMA_1974__23_132289,
     author = {P. Morel},
     title = {Sur le probl\`eme inverse des valeurs propres.},
     journal = {Numerische Mathematik},
     pages = {83--94},
     year = {1974},
     volume = {23},
     zbl = {0353.15017},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1974__23_132289/}
}