\documentclass{isodoc}
\usepackage{letter}
\setupdocument{
         to = {TeX Users Group\\
               1466 NW Naito Parkway, Suite 3141\\
               Portland, OR 97208-2311\\
               U.S.A
              },
     ourref = 1029,
 enclosures = isodoc documentation\\LPPL documentation,
     copyto = {Dutch TeX User group, NTG},
    subject = An example letter using the isodoc class --
		with an extra long subject extending over two lines.,
  autograph,foreign
}
\begin{document}
\letter[language=itIT]{
This letter was composed using the \LaTeX{} isodoc class. 
  \par\input{thuan} % for some body
}
\end{document}
