该natbib包有一个非常有用的选项merge，允许一个人在同一个编号下拥有两个或多个引用。对于以下简单代码，它工作得很好：
\documentclass[a4paper,english]{article}
\usepackage[cp1251]{inputenc}
\usepackage[T2A]{fontenc}
\usepackage[english]{babel}
\usepackage[a4paper]{geometry}
\usepackage{filecontents}
\begin{filecontents}{References.bib}
@article{Book1,
author = {M.~G. Author and T.~K. Author},
journal = {J. Opt. Soc. Am. A},
number = {7},
pages = {811--818},
title = {Article Title1},
volume = {71},
year = {1981}
}
@article{Book2,
author = {M.~G. Author and T.~K. Author},
journal = {J. Opt. Soc. Am.},
number = {17},
pages = {811--818},
title = {Article Title1},
volume = {11},
year = {1991}
}
\end{filecontents}
\usepackage[numbers, merge]{natbib}
\begin{document}
\cite{Book1, *Book2} %note merging "*" here (result: [1])
\bibliographystyle{plainnat}
\bibliography{References}
\end{document}
但是一旦我想在\thebibliography命令之后合并引用（例如，在附录中），它就不起作用：
\begin{document}
\bibliographystyle{plainnat}
\bibliography{References} %my *.bib file
\cite{Book1, *Book2} %(result: [1,2])
\end{document}
我怎么解决这个问题？