22 \(\mathbf{\sigma}\left(\mathbf{u}\mathrm{,}\varphi\mathrm{,}p\right)=g\left(\varphi,p\right)\frac{\partial{\psi_{e}}^{+}\left(\mathbf{\varepsilon}^{e}\right)}{\partial\mathbf{\varepsilon}^{e}}+\frac{\partial{\psi_{e}}^{-}\left(\mathbf{\varepsilon}^{e}\right)}{\partial\mathbf{\varepsilon}^{e}}\) ,