Benedetto - Spectral Synthesis - New paperback or softback - X555z

Birman - Spectral Theory - New paperback or softback - X555z

Bollobas - Modern Graph Theory - New paperback or softback - X555z

Helson - Spectral Theorem - New paperback or softback - X555z

Baggenstos - Graph Isomorphism Algorithms - New paperback or softback - X555z

Stevanovic - Spectral Radius of Graphs - New paperback or softback - X555z

Spectral Graph Theory by Fan R. K. Chung (1996, Trade Paperback)

Harris - Combinatorics and Graph Theory - New paperback or softback - - X555z