\begin{thebibliography}{Cx}
\markboth{\quad References \hfill}{\hfill References\quad}
\addcontentsline{toc}{chapter}{References}

\bibitem{Ar} Michael Artin, {\em Algebra}, Prentice Hall, Inc., Englewood
Cliffs, NJ, 1991

\bibitem{Bea} Alan F. Beardon, {\em The geometry of discrete groups},
Springer, New York, 1983

\bibitem{Bn} Roberto Bonola, {\em Non-Euclidean geometry: a critical and
historical study of its developments}, Dover, New York, 1955

\bibitem{ConSmi} J.H. Conway and D.A. Smith, On quaternions and octonions,
A.K.~Peters, Natick Mass., 2002

\bibitem{Cx} H.S.M.~Coxeter, {\em Introduction to geometry}, Wiley, 1969

\bibitem{Fn} Richard P. Feynman, {\em The Feynman lectures on physics,
Vol.~3: Quantum mechanics}, Addison-Wesley, Reading (Mass.), 1965

\bibitem{FH} William Fulton and Joseph Harris, {\em Representation theory, a
first course}, Springer, 1991

\bibitem{Gr} James A. Green, {\em Sets and Groups, a First Course in
Algebra}, Chapman and Paul, 1995

\bibitem{Gg} Marvin J. Greenberg, {\em Euclidean and non-Euclidean
geometries: development and history}, 3rd ed., W.H. Freeman, New York, 1993

\bibitem{Ha} Robin Hartshorne, {\em Geometry: Euclid and beyond},
Undergraduate Texts in Mathematics, Springer, New York, 2000

\bibitem{Hil} David Hilbert, {\em Foundations of geometry}, 2nd ed., Open
Court, LaSalle, 1971

\bibitem{Le} Walter Ledermann, {\em Introduction to the theory of finite
groups}, Oliver and Boyd, Edinburgh, 1964

\bibitem{Ln} Pertti Lounesto, {\em Clifford algebras and spinors}, C.U.P.,
1997

\bibitem{NSh} V.V.~Nikulin and I.R.~Shafarevich, {\em Geometries and
groups}, Springer Universitext, 1987

\bibitem{Rees} Elmer Rees, {\em Notes on geometry}, Springer, 1983

\bibitem{Ru} Walter Rudin, {\em Principles of mathematical analysis}, 3rd
ed., McGraw-Hill, New York, 1976

\bibitem{Se} Graeme Segal, {\em Lie groups}, in R.~Carter, G.~Segal and
I.G.~Macdonald, {\em Lectures on Lie groups and Lie algebras}, CUP/LMS
student texts, Cambridge, 1995

\bibitem{St} Shlomo Sternberg, {\it Group theory and physics}, CUP,
Cambridge, 1994

\bibitem{Su} W.A. Sutherland, {\em Introduction to metric and topological
spaces}, O.U.P.

\end{thebibliography}
