References
- Alonso, J. M., Brady, T., Cooper, D., Ferlini, V., Lustig, M., Mihalik, M., Shapiro, M., Short, H. (1991). Notes on word hyperbolic groups. In: Group Theory from a Geometrical Viewpoint. Proceedings of a Workshop, held at the International Centre for Theoretical Physics in Trieste, Italy, 26 March to 6 April 1990, pp. 3–63. Singapore: World Scientific.
- Bridson, M. R., Haefliger, A. (1999). Metric Spaces of Non-Positive Curvature, volume 319 of Grundlehren der mathematischen Wissenschaften [Fundamental Principles of Mathematical Sciences]. Berlin: Springer-Verlag.
- Chiswell, I. M. (1976). Abstract length functions in groups. Math. Proc. Cambridge Philos. Soc. 80:451–463. DOI: 10.1017/S0305004100053093.
- Culler, M., Morgan, J. W. (1987). Group actions on ℝ-trees. Proc London Math. Soc. Third Ser. 55:571–604. DOI: 10.1112/plms/s3-55.3.571.
- Culler, M., Vogtmann, K. (1986). Moduli of graphs and automorphisms of free groups. Invent. Math. 84:91–119. DOI: 10.1007/BF01388734.
- Lyndon, R. C. (1963). Length functions in groups. Math. Scand. 12:209–234. DOI: 10.7146/math.scand.a-10684.
- Parry, W. (1991). Axioms for translation length functions. In: Arboreal Group Theory. Proceedings of a Workshop, Held September 13–16, 1988, in Berkeley, CA (USA). New York: Springer-Verlag, pp. 295–330.