1. Brandt, A.: Multi-level adaptive solutions to boundary-value problems. Math. Comput.31, 333?390 (1977)
2. Brandt, A., Cryer, C.W.: Multigrid algorithms for the solution of linear complementarity problems arising from free boundary problems. MRC Technical Summary Report Nr. 2131, 1980
3. Fagé, D.M.: The Indicatrix Method in Free Boundary Problems. Numer. Math.38, 39?52 (1981) and Numer. Math.38, 255?261 (1981)
4. Hackbusch, W.: On the convergence of multi-grid iterations. Beiträge zur Numerischen Mathematik9, 213?239 (1981)
5. Hackbusch, W.: Introduction to the multi-grid methods for the numerical solution of boundary value problems. In: Computational Methods for Turbulent, Transonic, and Viscous Flows. Essers, J.A. (ed.). Hemisphere, Washington (to appear in 1983)