We start with the double-anchored matrix. The four point condition can be written in three ways, but only one of them is compatible with the tree T. Since we assumed w.l.o.g that \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ab.cd \in \mathcal {Q}^{T}$\end{document}ab.cd∈QT, the four point condition compatible with T is: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\begin{array}{*{20}l} \overbrace{D^{\prime}_{uv}[a,b]+D^{\prime}_{uv}[c,d]}^{L} &< \overbrace{D^{\prime}_{uv}[a,d] + D^{\prime}_{uv}[b,c]}^{R1} \\ &= \overbrace{D^{\prime}_{uv}[a,c] + D^{\prime}_{uv}[b,d]}^{R2}. \end{array} $$ \end{document}Duv′[a,b]+Duv′[c,d]⏞L<Duv′[a,d]+Duv′[b,c]⏞R1=Duv′[a,c]+Duv′[b,d]⏞R2.