V. Peller, “Factorization and approximation problems for matrix functions”, J. Amer. Math. Soc., 11, no. 4, 1998, 751
Dimitrios Chiotis, Zinaida A. Lykova, N. J. Young, “Exterior products of operators and superoptimal analytic approximation”, Trans London Maths Soc, 8, no. 1, 2021, 299
V.V. Peller, S.R. Treil, “Approximation by Analytic Matrix Functions: The Four Block Problem”, Journal of Functional Analysis, 148, no. 1, 1997, 191