1. Geometric inequalities;Burago,1988
2. A lower bound for the smallest eigenvalue of the Laplacian;Cheeger,1970
3. On relative isoperimetric inequalities in the plane;Cianchi;Bolletino U.M.I.,1989
4. The first eigenvalue of the Laplacian for the plane domains;Croke,1981
5. Der Satz vom Vektorbereich in Raümen beliebiger Dimension;Godbersen;Göttingen Diss.,1938