deletions | additions       diff --git a/header.tex b/header.tex  index ea2efc9..effa031 100644  --- a/header.tex  +++ b/header.tex 
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%\usepackage{amsmath}  \DeclareMathOperator{\sgn}{sgn} %\DeclareMathOperator{\sgn}{sgn} // signum function failed  \newtheorem{theorem}{Theorem}  \newtheorem{proof}{Proof}