[1] Abdelmoumen, B., Jeribi, A., Mnif, M.: 
Invariance of the Schechter essential spectrum under polynomially compact operator perturbation. Extr. Math. 26 (2011), 61-73. 
MR 2908391 | 
Zbl 1283.47007[3] Bhatia, R., Davis, C.: 
Perturbation of extended enumerations of eigenvalues. Acta Sci. Math. 65 (1999), 277-286. 
MR 1702207 | 
Zbl 0933.47015[6] Gil', M. I.: 
Lower bounds for eigenvalues of Schatten-von Neumann operators. JIPAM, J. Inequal. Pure Appl. Math. 8 (2007), Article ID 66, 7 pages. 
MR 2345921 | 
Zbl 1133.47016[9] Gil', M. I.: 
A bound for imaginary parts of eigenvalues of Hilbert-Schmidt operators. Funct. Anal. Approx. Comput. 7 (2015), 35-38. 
MR 3313254 | 
Zbl 1355.47011