[1] K.H. Forster and N. Hartanto, On the block numerical range of nonnegative matrices, Oper. Theory: Adv. Appl., 188 (2008), 113-133.
[2] K.E. Gustafson and D.K.M. Rao, Numerical range: The field of values of linear operators and matrices, Springer-Verlag, New York, 1997.
[3] R.A. Horn and C.R. Johnson, Matrix Analysis, Cambridge University Press, Cambridge, 1985.
[4] R.A. Horn and C.R. Johnson, Topics in Matrix Analysis, Cambridge University Press, Cambridge, 1991.
[5] J.N. Issos, The Field of Values of Non-Negative Irreducible Matrices, Ph.D. Thesis, Auburn University, 1966.
[6]H. Langer and C. Tretter, Spectral decomposition of some nonselfadjoint block operator matrices, J. Oper. Theory, 39(2) (1998), 339-359.
[7] C.K. Li, B.S. Tam and P.Y. Wu, The numerical range of a nonnegative matrix, Linear Algebra Appl., 350 (2002), 1-23.
[8] J. Maroulas, P.J. Psarrakos and M.J. Tsatsomeros, Perron-Frobenius type results on the numerical range, Linear Algebra Appl., 348 (2002), 49--62.
[9] H. Mink, Nonnegative Matrices, Wiley, New York, 1988.
[10] A. Salemi, Total decomposition and the block numerical range, Banach J. Math. Anal., 5(1) (2011), 51-55.
[11] C. Tretter and M. Wagenhofer, The block numerical range of an $ n\times n $ block operator matrix, SIAM J. Matrix Anal. Appl., 24(4) (2003), 1003--1017.
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