\documentclass[11pt]{scrartcl}

% vim: tw=50

\usepackage{notesheader}

{
\renewtheorem{customproposition}{Proposition}[section]
\renewtheorem{customtheorem}[customproposition]{Theorem}
\renewtheorem{customlemma}[customproposition]{Lemma}
\renewtheorem{customcorollary}[customproposition]{Corollary}
\renewtheorem{customexample}[customproposition]{Example}
\renewtheorem{customremark}[customproposition]{Remark}
}

\begin{document}

\newcommand\coursecode{GRM}
\title{Groups, Rings and Modules}
\author{}
\date{\today}
\maketitle

\tableofcontents

\newpage

\lecturelist

\newpage

\inputlectures

\end{document}