@article{IM_1983__74_143081,
     author = {Elliott H. Lieb},
     title = {On the lowest eigenvalue of the {Laplacian} for the intersection of two domains.},
     journal = {Inventiones mathematicae},
     pages = {441--448},
     publisher = {mathdoc},
     volume = {74},
     year = {1983},
     zbl = {0538.35058},
     url = {http://geodesic.mathdoc.fr/item/IM_1983__74_143081/}
}