1. M. Bercovier, O. Pironneau,Error estimates for finite element method solution of the Stokes problem in the primitive variables, Numer. Math.33 (1979), 211–224.
2. F. Brezzi,On the existence, uniqueness and approximation of saddle point problems arising from Lagrangian multiplers, RAIRO Anal. Numér.2 (1974), 129–151.
3. P. Clement,Approximation by finite element functions using local regularization, RAIRO Anal. Numér.9 R-2 (1975), 33–76.
4. M. Crouzeix, P. A. Raviart,Conforming and non-conforming finite element methods for solving the stationary Stokes equations, RAIRO Anal. Numér.7 R-3 (1977), 33–76.
5. M. Fortin,An analysis of the convergence of mixed finite element methods, RAIRO Anal. Numér.11 R-3 (1977), 341–354.