[closed] Fehler bei \maketitle

\documentclass{book}

\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}

\usepackage{graphicx}
\usepackage{microtype}
\usepackage{tabularx}
\usepackage{xcolor}

\usepackage[greek,russian,german,english]{babel}

\newtheorem{acknowledgement}{Acknowledgement}
\newtheorem{algorithm}{Algorithm}
\newtheorem{axiom}{Axiom}
\newtheorem{case}{Case}
\newtheorem{claim}{Claim}
\newtheorem{conclusion}{Conclusion}
\newtheorem{condition}{Condition}
\newtheorem{conjecture}{Conjecture}
\newtheorem{corollary}{Corollary}
\newtheorem{criterion}{Criterion}
\newtheorem{definition}{Definition}
\newtheorem{example}{Example}
\newtheorem{exercise}{Exercise}
\newtheorem{lemma}{Lemma}
\newtheorem{notation}{Notation}
\newtheorem{problem}{Problem}
\newtheorem{principle}{Principle}
\newtheorem{proposition}{Proposition}
\newtheorem{remark}{Remark}
\newtheorem{solution}{Solution}
\newtheorem{summary}{Summary}
\newtheorem{theorem}{Theorem}

\usepackage{makeidx}
\makeindex

\begin{document}

\frontmatter

\title{Classical Mechanics and Quantum Mechanics.\\
    \\
    An historic-axiomatic approach}

\author{Peter Enders}
\date{October, 2015}

\maketitle

\newpage

    Dedicated to my parents, Lieselott and Gerhart Enders

\chapter*{Foreword}
...
\printindex

\end{document}