1. Ionkin, N.I., Solution of a Boundary-Value Problem in Heat Conduction with a Nonclassical Boundary Condition, Differ. Uravn., 1977, vol. 13, no. 2, pp. 294–304. Engl. transl. in Differ. Equ., 1977, vol. 13, no. 2, pp. 204–211.
2. Il’in, V.A., Basis Property and Equiconvergence with the Trigonometric Series of Root Function Expansions and the Form of Boundary Conditions for a Nonself-Adjoint Differential Operator, Differ. Uravn., 1994, vol. 30, no. 9, pp. 1516–1529. Engl. transl. in Differ. Equ., 1994, vol. 30, no. 9, pp. 1402–1413.
3. Il’in, V.A. and Kritskov, L.V., Properties of Spectral Expansions Corresponding to Nonself-Adjoint Differential Operators, in Funktsional’nyi analiz. Itogi nauki i tekhn. Sovr. matematika i ee prilozheniya: Temat. obzor (Functional Analysis. Advances in Science and Engineering. Modern Mathematics and Its Applications. Featured Review), Moscow, 2006, vol. 96, pp. 190–231. Engl. transl. in J. Math. Sci. (NY ), 2003, vol. 116, no. 5, pp. 3489–3550.
4. Lomov, I.S., Nonsmooth Eigenfunctions in Problems of Mathematical Physics, Differ. Uravn., 2011, vol. 47, no. 3, pp. 358–365. Engl. transl. in Differ. Equ., 2011, vol. 47, no. 3, pp. 355–362.
5. Belyantsev, O.V. and Lomov, I.S., On the Basis Property of Eigenfunctions of a Singular Second-Order Differential Operator, Differ. Uravn., 2012, vol. 48, no. 8, pp. 1187–1189. Engl. transl. in Differ. Equ., 2012, vol. 48, no. 8, pp. 1174–1176.