by Didenko, Victor D., Silbermann, Bernd
Published in Journal of spectral theory (01.01.2021)

by Jiang, Zhi Jie
Published in Taiwanese journal of mathematics (01.10.2011)

by Ardalani, Mohammad Ali
Published in Taiwanese journal of mathematics (01.02.2014)

by Stević, Stevo, Jiang, Zhi Jie
Published in Taiwanese journal of mathematics (01.12.2011)

by Stevic, Stevo
Published in Applied mathematics and computation (01.04.2010)