1. A. Abian, The precise annulus containing all the zeros of a polynomial, Period. Math. Hungarica 14 (1983), 107–109.
2. M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, Dover, New York, 1972.
3. H.E. Bell, Gershgorin’s theorem and the zeros of polynomials, Amer. Math. Monthly 72 (1965), 292–295.
4. L. Berwald, Elementare Sätze über die Abgrenzung der Wurzeln einer algebraischen Gleichung, Acta Litt. Sci. (Szeged) 6 (1934), 209–221.
5. B. Bojanov, On an estimation of the roots of algebraic equations, Zastos. Mat. 11 (1970), 195–205.