deletions | additions       diff --git a/2QEnergies.tex b/2QEnergies.tex  index 5dc6bd9..eb412db 100644  --- a/2QEnergies.tex  +++ b/2QEnergies.tex 
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&=-\epsilon_{12}(nm)\delta_{sn}\delta_{tm}  \end{split}  \end{equation}  where $H_1=...$, $H_2=...$, $H_3=...$, $\epsilon_N=...$, $\epsilon_1=...$, $\epsilon_2=...$ and $\epsilon_{12}=...$. One can easily identify two diagonal terms and a off-diagonal one.