Grazie!
Scrivo di seguito quanto contenuto nel mio file:
\documentclass[a4paper,12pt]{book}
\usepackage[applemac]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{indentfirst}
\usepackage[italian]{babel}
\usepackage{fancyhdr}
\usepackage{showkeys}
\usepackage[dvips]{graphicx}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{latexsym}
\usepackage{amsthm}
\usepackage{eucal}
\usepackage{eufrak}
\usepackage{graphicx}
\pagestyle{fancy}\addtolength{\headwidth}{20pt}
\renewcommand{\chaptermark}[1]{\markboth{\thechapter.\ #1}{}}
\renewcommand{\sectionmark}[1]{\markright{\thesection \ #1}{}}
\cfoot{}
\rhead[\fancyplain{}{\bfseries\leftmark}]{\fancyplain{}{\bfseries\thepage}}
\lhead[\fancyplain{}{\bfseries\thepage}]{\fancyplain{}{\bfseries\rightmark}}
\usepackage{amsthm}
\theoremstyle{plain}
\newtheorem{thm}{Teorema}[section]
\newtheorem{cor}[thm]{Corollario}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{prop}[thm]{Proposizione}
\theoremstyle{definition}
\newtheorem{exmp}{Esempio}[section]
\theoremstyle{definition}
\newtheorem{defn}{Definizione}[chapter]
\theoremstyle{remark}
\newtheorem{oss}{Osservazione}
\begin{document}
%tesi
%Bibliografia
\begin{thebibliography} {99}
\addcontentsline{toc}{chapter}{Bibliografia}
\bibitem{} M. Curzio, P. Longobardi, M. Maj, \textit{Lezioni di algebra}, Liguori Editore, 1994.
\bibitem{D} D. S. Dummit, R. M. Foote, \textit{Abstract algebra}, John Wiley \& Sons, Inc., 2004.
\bibitem{I} I. M. Isaacs, \textit{Subgroups generated by small classes in finite groups}, Proc. Amer. Math. Soc. $\boldsymbol{136}$ (2008), 2299-2301.
\bibitem{Ma} A. Machì, \textit{Gruppi – Una introduzione a idee e metodi della Teoria dei Gruppi}, Springer, 2007.
\end{thebibliography}