我遇到了错误:
'Undefined control sequence
l.12 \setkomavar{subject}{Regarding: Code 123.456}'
我的文档序言如下:
\documentclass{letter}
\usepackage{hyperref}
\usepackage[english]{babel}
\signature{M.Y. Name}
\address{Street \\ Place \\ ZIP-code}
\begin{document}
\begin{letter}{Recipient \\ I know where your bed sleeps \\ I know where your house lives}
\setkomavar{subject}{Regarding: Code 123.456}
\opening{Dear Sir, Madam}
\end{letter}
\end{document}
什么地方出了错?