@article{10_1017_S0017089502010157,
     author = {Lamberti, Pier Domenico and Cristoforis, Massimo Lanza de},
     title = {An analyticity result for the dependence of multiple eigenvalues and eigenspaces of the laplace operator upon perturbation of the domain},
     journal = {Glasgow mathematical journal},
     pages = {29--43},
     year = {2002},
     volume = {44},
     number = {1},
     doi = {10.1017/S0017089502010157},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089502010157/}
}