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@article{MZ_1987__195_183670, author = {W. Allegretto}, title = {On the {Principal} {Eigenvalues} of {Indefinite} {Elliptic} {Problems.}}, journal = {Mathematische Zeitschrift}, pages = {29--36}, publisher = {mathdoc}, volume = {195}, year = {1987}, zbl = {0595.35040}, url = {http://geodesic.mathdoc.fr/item/MZ_1987__195_183670/} }
W. Allegretto. On the Principal Eigenvalues of Indefinite Elliptic Problems.. Mathematische Zeitschrift, Tome 195 (1987), pp. 29-36. http://geodesic.mathdoc.fr/item/MZ_1987__195_183670/