1. Numerical range of a matrix: some effective criteria;Ballantine;Linear Algebra and Appl.,1978
2. An off-axis circle criterion for the stability of feedback systems with a monotonic nonlinearity;Cho;IEEE Trans. Automatic Control,1968
3. Feedback Systems: Input-Output Properties;Desoer,1975
4. Fields of values of a matrix;Givens;Proc. Amer. Math. Soc.,1952
5. A Gersgorin inclusion set for the field of values of a finite matrix;Johnson;Proc. Amer. Math. Soc.,1973