- Yu. Netrusov, Yu. Safarov, “Weyl Asymptotic Formula for the Laplacian on Domains with Rough Boundaries”, Commun. Math. Phys., 253, № 2, 2005, 481

- Julian Haddad, Marcos Montenegro, “On differentiability of eigenvalues of second order elliptic operators on non-smooth domains”, Journal of Differential Equations, 259, № 1, 2015, 408

- M. van den Berg, “Heat content and Hardy inequality for complete Riemannian manifolds”, Journal of Functional Analysis, 233, № 2, 2006, 478

- Giuseppina Barletta, Andrea Cianchi, Vladimir Maz’ya, “Bounds for eigenfunctions of the Neumann p-Laplacian on noncompact Riemannian manifolds”, Advances in Calculus of Variations, 17, № 2, 2024, 319

- Rainer Hempel, “On the lowest eigenvalue of the Laplacian with Neumann boundary condition at a small obstacle”, Journal of Computational and Applied Mathematics, 194, № 1, 2006, 54

- V. I. Burenkov, P. D. Lamberti, M. Lanza de Cristoforis, “Spectral stability of nonnegative self-adjoint operators”, J Math Sci, 149, № 4, 2008, 1417

- L. E. Rossovskii, “On the spectral stability of functional-differential equations”, Math Notes, 90, № 5-6, 2011, 867

- Yu. Alkhutov, V. G. Maz’ya, “L 1,p –Coercitivity and Estimates of the Green Function of the Neumann Problem in a Convex Domain”, J Math Sci, 196, № 3, 2014, 245

- Davide Buoso, 176, Geometric Properties for Parabolic and Elliptic PDE's, 2016, 65

- Veronica Felli, Lorenzo Liverani, Roberto Ognibene, “Quantitative spectral stability for the Neumann Laplacian in domains with small holes”, Journal of Functional Analysis, 288, № 6, 2025, 110817
