1. J. Agler: An abstract approach to model theory, Surveys of some recent results in operator theory, Vol. II, 123, Pitman Res. Notes Math. Ser., 192, Longman Sci. Tech., 1988.
2. M. Augat, J.W. Helton, I. Klep, S. McCullough: Bianalytic Maps Between Free Spectrahedra, Math. Ann. 371 (2018) 883–959.
3. J.A. Ball, G. Groenewald, T. Malakorn: Structured noncommutative multidimensional linear systems. SIAM J. Control Optim. 44 (2005), no. 4, 1474–1528.
4. H. Bart, I. Gohberg, M. A. Kaashoek, A. C. M. Ran: Factorization of matrix and operator functions: the state space method, Operator Theory: Advances and Applications 178, Linear Operators and Linear Systems, Birkhäuser Verlag, Basel, 2008.
5. A. Barvinok: A course in convexity, Graduate Studies in Mathematics 54, American Mathematical Society, Providence, RI, 2002.