“…The stress function approach and the related complementary energy-based variational principles have been successfully applied in the finite element analysis of twodimensional elasticity problems, see, e.g., [2,[7][8][9]. For three-dimensional problems, however, no efficient finite element model exists, which is due mainly to the C 1continuity requirement for the second-order stress functions on the one hand, and to the structure of the zero-energy modes and the difficulties with their suppression for the case of first-order stress functions, on the other hand [10].…”