Linear Algebra and Its Applications
For Toeplitz operators acting on the vector Hardy space H-2 with definite or indefinite metric, the closure of the respective numerical range is completely described. In the definite case, some observations regarding its boundary are also made. (C) 2011 Elsevier Inc. All rights reserved.
Bebiano, N., & Spitkovsky, I. M. (2012). Numerical ranges of Toeplitz operators with matrix symbols. Linear Algebra and its Applications, 436(6), 1721-1726.