I can't write $\ell_1$ and other mathematics symbol in this cover letter:
what packages are needed?
\documentclass[a4paper,parskip=full,]{scrlttr2}
\usepackage[urw-garamond]{mathdesign}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{fontspec}
%\setmainfont{GaramondNo8}
%\setlength{\parindent}{0pt}
\usepackage{xcolor}
\usepackage[english]{babel}
\nonfrenchspacing
%\setkomavar{fromname}{Ole Nordmann}
%\setkomavar{fromaddress}{Storebakken 15 \\ 5500 Haugesund}
%\setkomavar{fromphone}{+47 5222 8183}
\makeatletter
\renewcommand*{\raggedsignature}{\raggedright}
\makeatother
\begin{document}
\begin{letter}{H.P. \\ K. N. Technology
Tehran, I. R. Iran
\\ Email Add.:}
\\ Tel: : }
%\KOMAoptions{fromphone=true,fromfax=false}
\setkomavar{subject}{COVER LETTER FOR SUBMISSION OF MANUSCRIPT}
%\setkomavar{date}
\opening{Dear Dear Editor,}
\closing{Sincerely}
%\encl{loan application, gift certificate for chocolate}
\begin{itemize}
\item[No.] 1:\\
\begin{tabular}{|l|r@{~}|c|@{~}l@{\qquad}|r|}
\hline
%& Column 1& Column 2\\\hline
Ful name& hatam84analysis@gmail.com \\\hline
Institution & ...\\\hline
Country & \\\hline
E-mail Address & \\\hline
\end{tabular}
\end{itemize}
\begin{itemize}
\item[No.] 2:\\
\begin{tabular}{|l|r@{~}|c|@{~}l@{\qquad}|r|}
\hline
%& Column 1& Column 2\\\hline
Ful name& ... \\\hline
Institution & ...\\\hline
Country & \\\hline
E-mail Address & \\\hline
\end{tabular}
\end{itemize}
\begin{itemize}
\item[No.] 3:\\
\begin{tabular}{|l|r@{~}|c|@{~}l@{\qquad}|r|}
\hline
%& Column 1& Column 2\\\hline
Ful name& ... \\\hline
Institution & ...\\\hline
Country & \\\hline
E-mail Address & \\\hline
\end{tabular}
\end{itemize}
\begin{itemize}
\item[No.]4:\\
\begin{tabular}{|l|r@{~}|c|@{~}l@{\qquad}|r|}
\hline
%& Column 1& Column 2\\\hline
Ful name& ... \\\hline
Institution & ...\\\hline
Country & \\\hline
E-mail Address & \\\hline
\end{tabular}
\end{itemize}
\end{letter}
\end{document}
$\ell$. – Johannes_B Aug 07 '14 at 08:39\closing{Sincerely}
– user60350 Aug 07 '14 at 08:42