\documentclass[a4paper,10pt]{article}

\usepackage[utf8]{inputenc}
\usepackage[russian]{babel}
\usepackage{ntheorem}
%\usepackage[active]{srcltx}

% Custom commands
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\title{Лекции по аналитической геометрии и линейной алгебре, 2 семестр}
\author{Репин О.Н., под редакцией Зайцева Ю.В.}

\begin{document}

\maketitle

\input{abstract}

\newpage 

\tableofcontents

\input{intro}

\input{ch1}
\input{ch2}


\end{document}
