1. [B] Brown, K.: Buildings. Berlin Heidelberg New York: Springer 1988
2. [BGSS] Baumslag, G., Gersten, S.M., Shapiro, M., Short, H.: Automatic groups and amalgams. J. Pure Appl. Algebra (to appear)
3. [BT] Bruhat, F., Tits, J.: Groupes réductifs sur un corps local. I. Données radicales valuées. Publ. Math., Inst. Hautes Étud. Sci.41 5?251 (1972)
4. [CEHPT] Cannon, J.W., Epstein, D.B.A., Holt, D.F., Patterson, M. S., Thurston, W.P.: Word processing and group theory. (University of Warwick preprint Jan. 1990)
5. M.S.R.I series;M. Gromov,1987