Some notes on the early history of hybrid stress finite element method

The "rst remark of this paper is to disclose a historical fact that the assumed stress hybrid "nite element method pioneered by Pian [1] in 1964 was actually developed originally based on the Hellinger}Reissner principle and not on the complementary energy principle as indicated in the published paper. The other remark is that Dick Gallagher was the "rst person to prove the fact that the rectangular plane stress elements by Pian is identical to the Turner element presented in 1956. Finally, through a formulation by Hellinger}Reissner principle a formal proof is given of the fact that the Pian element is also identical to Wilsonʹs incompatible element