2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\begin{array}{@{}rcl@{}} D^{\prime}_{v}[a,b] &=& \sum_{u \in \mathcal{L} - \{a,b,v\}} D^{\prime}_{uv}[a,b] \end{array} $$ \end{document}Dv′[a,b]=∑u∈ℒ−{a,b,v}Duv′[a,b]