[1] DRAGOMIR, S. S.: A survey of some recent inequalities for the norm and numerical radius of operators in Hilbert spaces, Banach J. Math. Anal. 1 (2007), no.2, 154–175. (Zbl 1136.47006, MR2366098.)
[2] DRAGOMIR, S. S.: Power inequalities for the numerical radius of a product of two operators in Hilbert spaces,Sarajevo J.Math. 5 (18) (2009), no. 2, 269–278. (Zbl 1225.47008, MR2567758.)
[3] DRAGOMIR, S. S.: Inequalities for the norm and numerical radius of composite operator in Hilbert spaces,In: Inequalities Applications, Internat. Ser. Numer. Math. Vol. 157, Birkhäuser, Basel, 2009. pp. 135–146. (Zbl 1266.26036, MR2758975.)10.1007/978-3-7643-8773-0_13
[4] GOLDBERG, M.—TADMOR, E.: On the numerical radius and its applications,Linear Algebra Appl. 42 (1982), 263–284. (Zbl 0479.47002, MR0656430.)10.1016/0024-3795(82)90155-0
[5] GUSTAFSON, K. E.—RAO, D. K. M.: Numerical Range, The Field of Values of Linear Operators and Matrices, Universitext, Springer-Verlag, New York, Inc., 1997. (Zbl 0874.47003, Zbl 0362.47001. MR1417493.)