1. Actualit\'{e}s Scientifiques et Industrielles [Current Scientific and Industrial Topics], No. 1337;Bourbaki, N.,1968
2. C. Caratheodory, Theory of functions, vol. 2, Chelsea, New York, 1960.
3. Pure and Applied Mathematics, Vol. 28;Carter, Roger W.,1972
4. Grundlehren der mathematischen Wissenschaften [Fundamental Principles of Mathematical Sciences];Conway, J. H.,1988
5. A note on subgroups generated by reflections in Coxeter groups;Deodhar, Vinay V.;Arch. Math. (Basel),1989