\bibitem{Br:97}
 {\sc D. Braess},
 {\em Finite Elements: Theory, Fast Solvers, and Applications in 
 Solid Mechanics},
 Cambridge University Press, New York, 1997.

\bibitem{BrSc:94}
 {\sc S. C. Brenner and L. R. Scott},
 {\em The Mathematical Theory of Finite Element Methods},
 Springer-Verlag, New York, 1994.

\bibitem{BrFo:91}
 {\sc F. Brezzi and M. Fortin},
 {\em Mixed and Hybrid Finite Element Methods},
 Springer-Verlag, New York, 1991.

\bibitem{Cia:78}
 {\sc P. G. Ciarlet}, 
 {\em The Finite Element Method for Elliptic Problems}, 
 North-Holland, New York, 1978.

\bibitem{GiRa:86}
 {\sc V. Girault and P. A. Raviart}, 
 {\em Finite Element Methods for Navier-Stokes Equations: Theory and 
      Algorithms}, 
 Springer-Verlag, New York, 1986.

\bibitem{Jo:86}
 {\sc C. Johnson}, 
 {\em Numerical Solution of Partial differential Equations by the
 Finite Element Method}, 
 Cambridge University Press, Cambridge, 1987.

\bibitem{StFi:73}
{\sc G. Strang and G. Fix},
{\em An Analysis of the Finite Element Method}, Pretice-Hall, 
Englewood Cliffs, New Jersey, 1973.