我在正文中引用\cite{calvet2001forecasting}, 但是出错,错误信息为
Undefined control sequence
1.5 \harvarditem
{Calvet and Fisher}{2001}{calvet2001forecasting}
我打开bbl文件如下
\begin{thebibliography}{1}
\newcommand{\enquote}[1]{``#1''}
\expandafter\ifx\csname natexlab\endcsname\relax\def\natexlab#1{#1}\fi
\harvarditem{Calvet and Fisher}{2001}{calvet2001forecasting}
Calvet, L. and A.~Fisher (2001), \enquote{{Forecasting multifractal
volatility},} {\em Journal of econometrics\/}, ~105, 27--58.
\end{thebibliography}
请问这该怎么解决?