1. Akbaş M.: On suborbital graphs for the modular group. Bull. London Math. Soc. 33(6), 647–652 (2001)
2. Akbaş, M.: The Normalizer of Modular subgroups. Ph.D. Thesis, University of Southampton, (1989)
3. Akbaş M., Başkan T.: Suborbital Graphs for the Normalizer of $${\Gamma _{0}(N)}$$ . Turkish J. Math. 20(3), 379–387 (1996)
4. Biggs, N.L., White, A.T.: Permutation groups and combinatorial structures. London Math. Soc. Lecture Note Ser. 33, CUP, Cambridge (1979)
5. Guler B.O., Besenk M., Deger A.H., Kader S.: Elliptic elements and circuits in suborbital graphs. Hacet. J. Math. Stat. 40(2), 203–210 (2011)