@article{CRMATH_2007__344_3_169_0, author = {Fran\c{c}ois Hamel and Nikolai Nadirashvili and Emmanuel Russ}, title = {Some isoperimetric problems for the principal eigenvalues of second-order elliptic operators in divergence form}, journal = {Comptes Rendus. Math\'ematique}, pages = {169--174}, publisher = {Elsevier}, volume = {344}, number = {3}, year = {2007}, doi = {10.1016/j.crma.2006.11.025}, language = {en}, }