1 Algebraic Graph Theory- Norman Biggs- ISBN 0 521 45897 8 -1996

2 Algebraic Graph Theory- Chris Godsil, Gordon Royle - ISBN 0 387 95220 9 - 2001

3 Spectra of Graphs Theory and application- Cvetkovic, Dragos M.; Doob, Michael; Sachs, Horst - ISBN 0 12 195150 2 - 1979