References on the Mathematical Structures Used in Quantum Mechanics:
E. Prugovecki, “Quantum Mechanics in Hilbert Space,” Dover, Mineola, New York, 2006
L. Debnath and P. Mikusinski, “Introduction to Hilbert Spaces with Applications,” 3rd Edition, Elsevier, Amsterdam, 2005
C. J. Isham, “Lectures on Quantum Theory,” Imperial College Press, London, 1995
A. Bohm, “Quantum Mechanics,” 3rd Edition, Springer, Berlin, 1993.