<math>x_{i_{\ell+1}} = \sum_{i_{\ell} \in \Omega} x_{i_{\ell}}, \quad d_{i_{\ell+1},j_{\ell+1}} = f^{-1}\left(\dfrac{\sum_{\substack{i_{\ell} \in i_{\ell+1}, j_{\ell} \in j_{\ell+1}}} \delta x_{i_{\ell}} x_{j_{\ell}} f(d_{i_{\ell},j_{\ell}})}{\sum_{\substack{i_{\ell} \in i_{\ell+1}, j_{\ell} \in j_{\ell+1}}} \delta x_{i_{\ell}} x_{j_{\ell}} }\right),\tag{12}</math> | <math>x_{i_{\ell+1}} = \sum_{i_{\ell} \in \Omega} x_{i_{\ell}}, \quad d_{i_{\ell+1},j_{\ell+1}} = f^{-1}\left(\dfrac{\sum_{\substack{i_{\ell} \in i_{\ell+1}, j_{\ell} \in j_{\ell+1}}} \delta x_{i_{\ell}} x_{j_{\ell}} f(d_{i_{\ell},j_{\ell}})}{\sum_{\substack{i_{\ell} \in i_{\ell+1}, j_{\ell} \in j_{\ell+1}}} \delta x_{i_{\ell}} x_{j_{\ell}} }\right),\tag{12}</math> |