Could you suggest a textbook for learning basic properties of spectrum of closed operators?

Question

I wish to learn the very basic properties of the spectrum of Closed operators. I may use these properties in the research in the Fluid dynamics/Differential equations.

My attempts:- I searched in google. Search was disappointing. I asked in Chat. I couldn't find the book.

I searched in the following textbooks

1. Textbook of Functional Analysis by V.K Krishnan[2E,PHI]
2. Functional Analysis-Balmohan Vishnu Limaye(2008, New Age International)
3. Foundations of Functional Analysis-Ponnusamy Saminathan (2002, Alpha Science International, Ltd_India Alpha) I couldn't find a basic theory related to the spectrum of closed operators. I request you to suggest a very basic textbook for learning this topic.

Answer 1

Introductory Functional Analysis With Applications, by Erwin Kreyszig , is a very good book for self learning in functional analysis and operator theory.