\documentclass[a4paper]{book}
\usepackage{amssymb,amsmath}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{graphicx}
%\graphicspath{{:Figure_Choice:}}
\usepackage[english,polutonikogreek,italian]{babel}

\providecommand{\boldsymbol}[1]{\mbox{\boldmath $#1$}}
\begin{document}

%\include{Corda1}
%\include{Fourier}
%\include{campi}
%\include{solidi}
%\include{Reticoli}
%\include{calore}
%\include{potterm}
\include{Fluidi}

\end{document}
