@article{MM2_1990__68_2_155528,
     author = {Brigitte Beekmann and Hermann L\"okes},
     title = {Estimates for the {Eigenvalues} of {Hill's} {Equation} and {Applications} for the {Eigenvalues} of the {Laplacian} on {Toroidal} {Surfaces.}},
     journal = {Manuscripta mathematica},
     pages = {295--308},
     publisher = {mathdoc},
     volume = {68},
     number = {2},
     year = {1990},
     zbl = {0733.34080},
     url = {http://geodesic.mathdoc.fr/item/MM2_1990__68_2_155528/}
}