1. Brill D., Flaherty F.,Isolated Maximal surfaces in spacetime, Comm. Math. Phys.,50 (1976), 157–165.
2. Choquet-Bruhat Y.,Maximal submanifolds and submanifolds with constant mean extrinsic-curvature of a Lorentzian manifold, Ann. Scuola Norm. (4),3 (1976), 361–376.
3. Choquet-Bruhat Y., Fisher A. E., Marsden J. E.,Maximal hypersurfaces and positivity of mass, (preprint).
4. Choquet-Bruhat Y., Leray J., Compt. Rend., 274, série A, 1972, p. 81.
5. Gilbarg D.,Boundary value problems for non linear elliptic equations in n variables in non linear problems, Madison, Wis, University of Wisconsis Press, 1963, 151–159.