Fritz Gesztesy, Nigel J. Kalton, Konstantin A. Makarov, Eduard Tsekanovskii, Operator Theory, System Theory and Related Topics, 2001, 271
Pavel Kurasov, Boris Pavlov, Operator Theory and Related Topics, 2000, 225
H. Langer, A. Markus, V. Matsaev, C. Tretter, “A new concept for block operator matrices:the quadratic numerical range”, Linear Algebra and its Applications, 330, no. 1-3, 2001, 89
N. T. Bagraev, A. B. Mikhailova, B. S. Pavlov, L. V. Prokhorov, A. M. Yafyasov, “Parameter regime of a resonance quantum switch”, Phys. Rev. B, 71, no. 16, 2005, 165308
A. Yu. Konstantinov, “Spectral analysis of one class of matrix differential operators”, Funct Anal Its Appl, 31, no. 3, 1997, 209
A. Yu. Konstantinov, “Spectral theory of some matrix differential operators of mixed order”, Ukr Math J, 50, no. 8, 1998, 1212
A. B. Mikhaylova, B. S. Pavlov, Operator Methods in Ordinary and Partial Differential Equations, 2002, 287
Alexander Konstantinovich Motovilov, “Альтернативное доказательство априорной $\operatorname{tg}\Theta$-теоремы”, Теоретическая и математическая физика, 186, no. 1, 2016, 101
Tobias Kusche, Reinhard Mennicken, Manfred Möller, “Friedrichs extension and essential spectrum of systems of differential operators of mixed order”, Mathematische Nachrichten, 278, no. 12-13, 2005, 1591
Reinhard Mennicken, Alexander K. Motovilov, “Operator Interpretation of Resonances Arising in Spectral Problems for 2 × 2 Operator Matrices”, Mathematische Nachrichten, 201, no. 1, 1999, 117