I've been learning moderncv to prepare my CV since the beginning of last year, yet I am not quite familiar with the details.
I have included in my resume a section "referees" using the code suggested by other users. It worked perfectly in the past but it seems some of the code is currently outdated and the code is not functioning. Whenever I compile the code I receive the following message:
! Undefined control sequence. <argument>
\listdoubleitemmaincolumnwidth
So I guess the problem lies in the above argument but I am probably wrong.
Here is an example:
\documentclass[11pt,a4paper,sans]{moderncv}
%% ModernCV themes
\moderncvstyle{casual}
\moderncvcolor{blue}
\renewcommand{\familydefault}{\sfdefault}
\nopagenumbers{}
%% Character encoding
\usepackage[utf8]{inputenc}
%% Adjust the page margins
\usepackage[scale=0.75]{geometry}
%% Personal data
\firstname{John}
\familyname{Doe}
\title{Resumé title (optional)}
\address{street and number}{postcode city}
\mobile{+1~(234)~567~890}
\phone{+2~(345)~678~901}
\fax{+3~(456)~789~012}
\email{john@doe.org}
\homepage{www.johndoe.com}
\extrainfo{additional information}
\photo[64pt][0.4pt]{picture}
\quote{Some quote (optional)}
%%------------------------------------------------------------------------------
%% Content
%%------------------------------------------------------------------------------
\begin{document}
\makecvtitle
\section{Education}
\cventry{year--year}{Degree}{Institution}{City}{ \textit{Grade} }{Description} % arguments 3 to 6 can be left empty
\cvitem{title}{ \emph{Title} }
\cvitemwithcomment{Language 1}{Skill level}{Comment}
\cvdoubleitem{category X}{XXX, YYY, ZZZ}{category Y}{XXX, YYY, ZZZ}
\cvlistitem{Item 1}
\cvlistdoubleitem{Item 2}{Item 3}
%% ...
%% A publications list
\nocite{*}
\bibliographystyle{plain}
\bibliography{publications} % a bibtex file containing the list of publications
\section{Referees}
\newcommand{\cvdoublecolumn}[2]{%
\cvline{}{%
\begin{minipage}[t]{\listdoubleitemmaincolumnwidth}#1\end{minipage}%
\hfill%
\begin{minipage}[t]{\listdoubleitemmaincolumnwidth}#2\end{minipage}%
}%
}
\newcommand{\cvreference}[7]{%
\textbf{#1}\newline% Name
\ifthenelse{\equal{#2}{}}{}{\addresssymbol~#2\newline}%
\ifthenelse{\equal{#3}{}}{}{#3\newline}%
\ifthenelse{\equal{#4}{}}{}{#4\newline}%
\ifthenelse{\equal{#5}{}}{}{#5\newline}%
\ifthenelse{\equal{#6}{}}{}{\emailsymbol~\texttt{#6}\newline}%
\ifthenelse{\equal{#7}{}}{}{\phonesymbol~#7}}
\cvdoublecolumn{\cvreference{Nicolai Reshetikhin}
{Department of Mathematics}
{University of California}
{Berkeley, CA 94720-3840}
{}
{reshetik@math.berkeley.edu}
{510-643-6234}%
}
{\cvreference{Mikhail Khovanov}
{Department of Mathematics}
{Columbia University}
{990 Broadway}
{New York, NY 10027}
{khovanov@columbia.edu}
{212-854-4186}%
}
\end{document}


\documentclass{...}and ending with\end{document}. – ChrisS Jan 01 '17 at 10:47