`\documentclass[a4paper,11pt,twoside]{article}
\usepackage{graphicx}
\usepackage{booktabs}
\usepackage[latin1]{inputenc}
\usepackage[english]{babel}
\usepackage{amsfonts}
\usepackage[round,sort]{natbib}
\setlength{\parindent}{0.70cm}
\usepackage{bm}
\newcommand{\primo}{\mathsf T}
\textwidth 12.5cm
\usepackage{caption}
\captionsetup{font=bf}
\usepackage{array}
\usepackage{widetable}
\textheight 18.5cm
\usepackage[T1]{fontenc}
\usepackage{textcomp}
\usepackage{txfonts}
\usepackage{mathptmx}
\usepackage{color}
\usepackage{guit}
\usepackage{url}
\makeatletter
\renewcommand\section{\@startsection {section}{1}{\z@}%
{1\baselineskip \@plus .2\baselineskip \@minus .1\baselineskip}%
{.5\baselineskip \@plus.1\baselineskip}%
{\normalfont\bfseries}}
\renewcommand\subsection{\@startsection {subsection}{1}{\z@}%
{1\baselineskip \@plus .1\baselineskip \@minus .05\baselineskip}%
{.2\baselineskip \@plus .05\baselineskip}%
{\normalfont\small\bfseries}}
\renewcommand\@seccntformat[1]{\csname the#1\endcsname.\hspace{0.2cm}} %o.2 è la distanza fra numero di sezione e titolo
\makeatother
\begin{document}`
e alla fine
`
\addcontentsline{toc}{section}{\refname}
\bibliographystyle{natbib}
\bibliography{biblio}`