@article{BUMI_2004_8_7B_1_a6,
     author = {Fleckinger, J. and Hern\'andez, J. and Th\'elin, F.},
     title = {Existence of multiple principal eigenvalues for some indefinite linear eigenvalue problems},
     journal = {Bollettino della Unione matematica italiana},
     pages = {159--188},
     publisher = {mathdoc},
     volume = {Ser. 8, 7B},
     number = {1},
     year = {2004},
     zbl = {1117.35054},
     mrnumber = {125307},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/BUMI_2004_8_7B_1_a6/}
}