1. Cannon, I.R., The Solution of Heat Equation Subject to the Specification of Energy, Quart. Appl. Math., 1963. vol. 21, no. 2, pp. 155–160.
2. Kamynin, L.I., A Boundary Value Problem in the Theory of Heat Conduction with Nonclassical Boundary Conditions, Zh. Vychisl. Mat. Mat. Fiz., 1964, vol. 4, no. 6, pp. 1006–1024.
3. Ionkin, N.I., The Solution of a Boundary Value Problem of the Theory of Heat Conduction with a Nonclassical Boundary Condition, Differ. Uravn., 1977, vol. 13, no. 2, pp. 276–304.
4. Il’in, V.A., Existence of a Reduced System of Eigen- and Associated Functions for a Nonself-Adjoint Ordinary Differential Operator, Tr. Mat. Inst. Steklova, 1976, vol. 142, pp. 148–155.
5. Keldysh, M.V., On the Eigenvalues and Eigenfunctions of Some Classes of Nonself-Adjoint Equations, Dokl. Akad. Nauk SSSR, 1951, vol. 77, no. 5, pp. 11–14.