Zavorokhin G.L., Nazarov A.I., Nazarov S.A., “The Symmetric Mode of An Elastic Solid Wedge With the Opening Close to a Flat Angle”, Dokl. Phys., 63:12 (2018), 526–529
S. A. Nazarov, “Finite-Dimensional Approximations of the Steklov–Poincaré Operator for the Helmholtz Equation in Periodic Waveguides”, J Math Sci, 232:4 (2018), 461