1. The patch test—a condition for assessing FEM convergence
2. The patch test for mixed formulations
3. The finite element method with Lagrangian multipliers
4. ‘On the existence, uniqueness and approximation of saddle point problems arising from Lagrange multipliers’, RAIRD, 8(r-2), 127-151 (1974).
5. and . ‘Mixed finite element methods and reduced and selection integration techniques; a unification of concepts’. Comp. Math. Appl. Mech. Eng., p. 5 (1978).