“…The studies of Steklov-type eigenvalue problems are related to several important problems in differential geometry, see for examples, [13,14,35,17,18]. They are also closely connected with some classical geometric inequalities and Sobolev trace inequalities, see [12,14,31,32,36,37,43,44]. It is also wellknown that the Dirichlet to Neumann map is an essential tool for studies of many inverse problems.…”