ϕ I = min f ∈ f ⊥ i ( ϕ f ) {\displaystyle \phi _{I}=\min \limits _{{\textit {f}}\in {\textit {f}}\perp i}(\phi _{f})}
∏ 0 < i < m 0 < j < n P ( i , j ) {\displaystyle \displaystyle \prod _{\begin{array}{c}0<i<m\\0<j<n\end{array}}P(i,j)}
