1. Computing the hyperbolicity constant
2. Hyperbolicity and complement of graphs
3. Gromov hyperbolic graphs
4. B.H. Bowditch,Notes on Gromov's hyperbolicity criterion for path-metric spaces, in Group Theory from a Geometrical Viewpoint, Trieste, 1990, E. Ghys, A. Haefliger and A. Verjovsky, eds., World Scientific, River Edge, NJ, 1991, 64–167.