1. Bannai E., Ito T.: Algebraic Combinatorics. I: Association schemes. The Benjamin/Cummings Publishing, Menlo Park (1984).
2. Biggs N.: Algebraic Graph Theory, 2nd edn. Cambridge Mathematical Library. Cambridge University Press, Cambridge (1993).
3. Bose R.C., Shimamoto T.: Classification and analysis of partially balanced incomplete block designs with two associate classes. J. Am. Stat. Assoc. 47, 151–184 (1952).
4. Brouwer A.E., Cohen A.M., Neumaier A.: Distance-Regular Graphs. Ergebnisse der Mathematik und ihrer Grenzgebiete (3) [Results in Mathematics and Related Areas (3)], vol. 18. Springer-Verlag, Berlin (1989).
5. Cameron P.J.: Combinatorics: Topics, Techniques, Algorithms. Cambridge University Press, Cambridge (1994).