The Asymptotic Behavior of the Solutions of the Wave Equation Concentrated near the Axis of a Two-Dimensional Waveguide in an Inhomogeneous Medium -- §1. A Waveguide in an Inhomogeneous Medium -- §2. The Construction of the Solutions of the Wave Equation Concentrated near the Waveguide Axis -- §3. The Asymptotic Behavior of the Eigenfunctions and Eigenvalues of the Boundary Problem for the Waveguide -- Literature Cited -- Perturbations of the Spectrum of the Schroedinger Operator with a Complex Periodic Potential -- §1. Preliminary Information -- §2. Investigations of the Perturbed Operator -- §3. Investigation of the Spectrum under the Condition $$\int{\left/ \text{q}\left( \text{x} \right) \right/}{{\text{e}}^{\text{ }\!\!\delta\!\!\text{ }\left/ x \right/}}dx$$ < ? -- §4. Proof That There Are No Eigenvalues on the Continuous Spectrum -- Literature Cited -- The Discrete Spectra of the Dirac and Pauli Operators -- §1. Auxiliary Information -- §2. The Discrete Spectrum of the Dirac Operator in the Case of Spherical Symmetry -- §3. The Discrete Spectrum of the Dirac Operator in the Three-Dimensional Case -- §4. The Discrete Spectrum of the Pauli Operator -- Literature Cited -- The Nonself-Adjoint Schroedinger Operator. III -- §1. Auxiliary Information -- §2. The Operator with Potential q(x) ? S? -- §3. The Operator with Potential q(x) ? Sn, n < ? -- Literature Cited -- The Singular Numbers of the Sum of Completely Continuous Operators -- Literature Cited -- Double-Integral Operators in the Ring R^ -- Literature Cited -- Correction to "The Inverse Problem in the Theory of Seismic Wave Propagation".