References
- Bridson M.R. private communication
- Dicks , W. and Dunwoody , M.J. 1989 . Groups acting on Graphs . Cambridge Studies in Advanced Mathematics , 17
- Ghys , E. and De La Harpe , P. 1990 . Sur les Groupes Hyperboliques d'apres Mikhael Gromov Birkhäuser Progress in Mathematics Series
- Harary , F. 1969 . Graph Theory , Addison-Wesley .
- Serre , J.P. 1980 . Trees , Springer-Verlag .